I have used both (7D a lot, 650D --which I think is the same as Rebel T4i-- a little, wife has it).
For sports or other kind of action shooting, I wouldn't think twice: 7D has way better AF, faster frame rate and superior ergonomics.
Th 650D has advantages in video (live AF, flexible LCD), and flexible LCD can be useful for other purposes as well (especially macro), but that's about it. Oh yeah, there's the touchscreen, if you care about that. And it is smaller and lighter (which is why my wife likes it).
Image quality is all but identical; the 650D has a slight advantage in JPG processing, but if you shoot raw you can't tell them apart.