I've been a little unimpressed with the video sharpness from my Canon T3i body since I've had it. I recently determined that, likely due to constant-bitrate encoding, the specific condition causing shots to look muddled is complexity: shots of a cat or a rock may be quite sharp, but moving leaves and ripples on water are apparently too much to describe frame to frame.
I had read that the 7d has been used for several high-end movies as well as lots of commercials and shorts, so that was my go-to comparison. I was initially confused however as the T3i and 7d share almost all specs, especially related to video; both use the same APS-C sized sensor, both use
4:2:2 chroma subsampling, and both produce ~45mbit
constrained baseline h.264 streams at 1080p and 29.97 fps. The only difference that I've been able to ascertain is that the 7d has two
DIGIC 4 processors, whereas the T3i has but one.
When my rented 7d arrived, I took both cameras with my to the pond near my house and shot some identical footage. It sure appears there is a difference:
My only guess is that, with two processors, the 7d is able to spend more time encoding the video stream and as such does a better job of the task. Now that I know the 7d is in fact sharper, I've sold my T3i body and purchased a used 7d. When it arrives, I hope to do some more side-by-side shots to compare settings so as to conclusively determine the best settings for my shots.
For what it's worth, the other main difference between the 7d and T3i is the autofocus: the 7d is worlds better. This isn't relevant for video since Canon bodies don't support constant autofocus during video, but for stills I appreciated it immediately. The 7d's high ISO noise may be slightly lower than the T3i but I didn't do an objective, controlled test.