The 1DmkIV is more responsive than the 7D for sure, but other than the faster frame rate and slightly better IQ, I don't know if the extra cost is justifiable. I would say AF tracking performance is about the same from my experience. The camera is more customizable so it can take longer to set up for what you need it to do, but it can work well once it is. I can bring one out for you to try - I'm free on Sunday and some weekday evenings.
.....I'll also bring a Nikon D4 so you can see how shitty the 1DmkIV is.