I have Reva flats and I have a pair of the zebra haircalf Kendrick drivers. For me personally, I found the Kendrick drivers to be more comfortable than my Revas.
Before I purchased my Kendricks, I looked up reviews because I couldn't really find any information about their comfort or sizing. Nordstrom had a bunch of reviews for the leather Kendricks.
I have found that my Revas have all gotten more comfortable over time but they were never very uncomfortable. I was also the same size in both Revas and the Kendrick drivers.
Right out of the box the Kendrick loafers are very comfy and require no breaking period. But I must agree with MJDaisy, the Reva flats are much cuter and aesthetically pleasing even though they do take some time to break in. But I do love them both