I've shot with the 7dm2 as my primary and 5dm3 as my backup for a football game recently. I thought the 7dm2 was just fantastic sports camera. Purchased the 7dm2 because I needed a second body for sports anyway and I wasn't entirely convinced that 4fps more was going to result in a huge difference. However, after having shot the game, I definitely have a bit more respect for the 10fps on the 7dm2. It's no joke and came away very impressed.
I thought the AF was slightly snappier than the 5dm3 as well although I have no scientific proof of that. In general, I got about 70% keepers with the 7dm2 versus 40% keepers for the 5dm3 when it comes to the action shots so I had no regrets with my purchase especially for good price from the CPW deal.
Two caveats: The game I shot kicked off at noon so even though I kept the 7dm2 at auto ISO, it shot everything at ISO 100. Didn't have a chance to compare high ISO noise between the two cameras.
One other caveat is that all my sports images are web-use only so far and I don't have to print them out into a giant poster or anything like that so I don't pixel peep and compare noise and IQ.
With all that said, if you shoot more sports/action than not, I'd go with 7dm2. For $1599, I think it's a great value as a general DSLR and even better for sports/action. Otherwise, I'd go with 5dm3 if you can get a good deal on it. To be honest, I don't really think you can go wrong with either, I think you would be able to make both cameras work for you.