Since I am a Bentley colleague I will refrain from telling you which is the best BIM platform (I think you could guess what my answer would be), but I will try to address a couple of your concerns and share some things to consider in your BIM evaluation for your firm. Obviously there is no software package in the world that is perfect, and Bentley does not claim to be exempt from that claim. We recognize we have deficiencies and work hard to erase those and also respond to user feedback in a timely manner. I would find it difficult to believe that you would hear claims from Revit users that they have the direct communication with Product Managers and developers like that occurs every day between Bentley and our clients. While at times some of the comments and posts that occur in BE Communities forums seem critical of some tools or applications, I firmly believe that the users in these forums feel comfortable posting their opinions (good or bad), because they are heard by Bentley product managers, developers, support and even the Bentley executives. Often times this result in a quick turn-around on a bug fix or additional features added to builds to meet a particular clients need. On the other hand, I have been told by several dual-platform clients that Revit's feature list is frozen for the 2014 release already (and closing in on feature freeze for 2015), therefore any feature requests or complaints on an Autodesk forum would be done so in vain. I really only mentioned that because I don't think that I have ever come across a person who confused Bentley with being arrogant, and I hope the users in this forum will reinforce this sentiment.
Regarding your concerns about Bentley, I would encourage you to take a look at AECOsim Building Designer rather than Bentley Architecture. Building Designer will be the next release (1-2 months away) of Bentley Architecture. However, for me to say that Building Designer is just the next version of Bentley Architecture is a gross understatement. Building Designer is a complete BIM solution in a single application that in addition to added architectural features includes full functionality for Structural, Mechanical, Plumbing, and Electrical design/documentation, a robust and intuitive clash detection engine, hyper-modeling, Dynamic Views, and additional feature enhancements. This is what you should be using as your benchmark against other BIM vendors.
If only looking at Bentley Architecture, I believe that your concern with poor 'help' documentation is valid, and as I stated above, Bentley has identified this as a shortcoming and invested in a thorough update to both the content and delivery methods of help/informational documentation that will ship with AECOsim Building Designer. In addition to this, an even bigger effort was initiated to overhaul the Bentley delivered datasets to make Building Designer production-ready with little-to-no customization required by the end user. This effort was guided by several of our BIM consultants with experience working everyday with our users from all over the world to capture the functional requirements of a vast user base and reflect the collective knowledge gained from this user collaboration into a workspace that everyone can leverage. The dataset overhaul was in direct response to user comments that the applications were complex (as you observed) and aimed to set out to show users that the solutions and workflows can be simple, while still affording the ability to customize the applications, workspaces, and processes to support even the most complex organizations, which in my opinion has always been one of Bentley's greatest strengths.
In my architecture days before Bentley I was faced with the same choice, which BIM solution is best for me and my organization. Given that I am now working for Bentley it is apparent which I chose, but I at time I was an more of an Autodesk user than Bentley if that indicates that I haven't been biased my entire BIM career. In fact, still to this day I have nearly as much experience on Autodesk applications as on Bentley applications. Full disclosure out of the way... Below I will include a couple points that you should consider in your evaluation as they are often overlooked items. At firms that I have worked for or consulted with, I have seen the workflow/staffing impact that oversight of these items has yielded and more importantly to a business the resultant hidden project and organizational costs, which are often substantial.
Interoperability - Bentley BIM solutions are all built on top of the DGN file format and thus there is no file export process required to move between 3D data-rich models and static 2D construction drawings that can be opened by clients, contractors, or reviewers that do not have Revit or Archicad. Additionally, since BIM is an intra-disciplinary process that requires intense collaboration by all project stakeholders (architects, engineers, contractors, owners, and more), Building Designer, as a unified BIM application, enables live referencing of models from all disciplines with full data fidelity to offer an immense project savings on avoiding data/time loss on import/export/link processes that can stall the design process. Bentley even provides a free plug-in that allows collaborators that might be working in Revit to publish i-Models (with precise geometry and BIM data) that can be referenced directly by MicroStation, Bentley BIM solutions, and even Navigator for Clash Detection and Design Review processes. Don't be mislead by Autodesk's claim that they allow direct linking of DGN's in Revit 2012 as an interoperable solution. Despite Autodesk having the DGN file format as part of the interoperability agreement between Autodesk and Bentley, they only allow a Revit link to a V7 DGN, which would require a Save As or Export, which disrupts live coordination and wastes project time and money on data exchange processes for your company.
BIM is a Collaborative Process.... Many people falsely assume that the main point of BIM from a design perspective is to simply have better coordinated 2D Construction documents, because they are extracted from the 3D model. While this is a benefit of BIM, anyone that identifies this as the primary reason to adopt BIM is clearly missing the point of the BIM process and is likely to not benefit much, if any, when it comes to the bottom line after additional software, training, and related overhead costs are factored in. BIM (as a process) should be utilized in conjunction with BIM software in order to produce a better designed (thoroughly coordinated across all disciplines & being free of costly, last minute coordination changes that compromise the overall design) & constructed built asset (reduced/eliminated change orders as a result of design phase coordination, among others) for the owner. BIM applications that nearly force you to work through a building as though it was a set of 2D drawings rather than a 3D facility (which needs to be inhabited, operated, and maintained in a 3D world) seem to be missing this critical component to the success of BIM, and the primary reason that owners are starting to more frequently require BIM. Personally, I have never physically experienced a building through plan, section, or elevation and as such can't understand how a designer would want to design a project in this manner when a 3D simulation model is being created. This is not something to be taken lightly, because as an architect or engineer you are not contracted to create pretty drawings that state it is someone else's problem, but instead you are to produce a coordinated design that will satisfy the functional requirements of the building program, codes, and owner's requirements. Also, if collaborating across offices, make sure to examine the process for sharing data/models as well as communicating design coordination information. Beware of being required to align software versions with all project consultants, which may result in users having to have multiple software versions on their machine at the same time in order to work on more than one project.
Infrastructure... Make sure to examine the system requirements carefully to avoid an unexpected overhaul of hardware in your office. In addition to just the computer hardware look at network bandwidth. I have seen a dual platform firm deploy Revit after doing a small pilot project (project approx. 20% of their normal project size), and as soon as they had a project of normal size they discovered they needed all new hardware and still the software had difficulty handling the complexity and size of the project. Upon bringing a second Revit project into the office the network was nearly crippled for most of the work day, and users had to begin to save to Central 30 minutes before they wanted to leave for the day. This resulted in the company being forced to upgrade their entire network, which combined with the hardware upgrades resulted in hidden costs that were greater than the software licenses (not even quantifying lost productivity into that amount). This experience is not intended to cut down Revit, just to warn you of what they won't tell you until after they have your money, if they tell you at all. Historically, Bentley's federated approach to workspaces and model organization has allowed numerous firms to save substantially by not requiring hardware or network upgrades and I would recommend that be considered in your evaluation.
As a BIM consultant, I work with users every day, and I think that you will see that most of the time despite the fact that I am a Bentley colleague that I will side with the user on topics related to functionality change requests, but at the same time tirelessly respond to user's inquiries with software questions and workflows that make BIM teams more profitable. It is with this experience in mind that I challenge you to look at a project's overall BIM workflow involving not just those that touch the BIM software, but the entire project team. I will tell you that making the transition to BIM is a challenging and potentially expensive one that involves substantial workflow/cultural changes in order to be most successful and maximize your return. Any software vendor that tries to sell a BIM solution without recognizing the need to interoperate with not only other disciplines, but also other vendors is not painting the entire picture for you and you will discover that cumbersome workflows for collaboration along with losses in time and data due to poor interoperability workflows are exponentially more costly with BIM than they are with CAD.
Well despite what this lengthy post might make you believe, I am a professional services consultant and not a marketing or sales guy, but I too often see the marketplace get consumed by the marketing machine of Autodesk that fails to tell the BIM story. I apologize if any comparisons seemed limited to Revit/Bentley that is only because I have limited experience with Archicad as most clients i work with are multi-disciplinary and mandate a BIM suite that includes capabilities for all engineering disciplines. If you would like any additional information regarding AECOsim Building Designer (or any of our products, preferably somewhat related to buildings), or if you would like more information on the BIM process, feel free to send me an email.
Now I will let the rest of the community chime in with their less-biased opinions. ;)