While 720/60 would be a VERY nice update...IMO, 720 looks less than good on my 7d. For slow-motion shots, it's usable...for extended shooting, you may as well be shooting SD when it comes down to the true resolving power of the camera.
1080 is pretty much mandatory to shoot with in order to achieve the HD "Pop" from the 7d. No experience (obviously
) with the 1d4 yet...but I shoot a ton of 720 with my HVX. The 7d looks muddy in comparison.
As far as processor intensive though, 1080 takes the cake. From what I've read about the second processor on the 7d...it's mainly, if not strictly for the new AF system. The 5d2
should be able to handle 720/50p and 60p.
I'll be happy though with 30p conforming to the standard 29.97 and the addition of 24p on 1080! That'll do it for me
J