I prefer the Live Display button on the Mk2 to the horrible switch on the Mk3 - but apart from that, most features of the Mk3 are vastly improved over the Mk2 (for my work).

I much prefer the location of the Mk3's Video Record button - just perfect.

I much prefer the location of the Mk3's Video Record button - just perfect.I 100% disagree. I have been using the 5D2 for 3+ years & the start/stop button falls very naturally under my thumb. It's far more fiddly to hit the small button higher up the 5D3.