What are the ramifications of updating to Connect U13 from U10

I have read about the performance improvements of U13.  I would like to update to that version but am concerned about the impact it may have for our work and the client that is still using U10.

Our concerns are that there may be fundamental changes to files between the two update versions specifically if we are using U13 and we are returning files to the client still using U10.

Can anyone shed light on this and any other issues this may include?