I use the 24 L II on a 1d4 (1,3x crop) and it's the perfect lens for my uses, I use it for EVERYTHING. Absolutely perfect.
Now, I'm moving on to a 1d X when it gets here, so I tried the 35 L on a 5d to sort of match the focal of 31mm the 24 gives on the mk4, BUT that is quite a lot narrower, even though it's only 4mm, it surprised me. So I went on to try the 24 on the 5d, and seems better, so I would have liked a 30mm on FF, but I'm much rather keeping the 24 than getting the 35 to replace it. This is also something to do with the fact that I have a 50 for a little more reach which I like MUCH better on FF than 1,3 crop.