This is mainly from a video use perspective, but:
I personally think the 600D has better video options than the 650D. Yes the 650D has autofocus, but thats really only use able with the STM lenses and even with an STM lens its not brilliant. Your far better using manual focus.
Also withthe 600D you can do a 3x digital zoom in camera which gives almost the same video quality. You can't do this with the 650D.
Other than a digital zoom what else is there? Can't say I've used my 650d for any video other than a few tests so I don't really know what might be missing.
I see a lot of negative or indifferent comments about the touchscreen but I really do think it's great. I wouldn't want all the buttons to go altogether but having both button and the screen is good imo. I'd imagine all cameras will have touchscreens eventually because why wouldn't they? If you can have buttons and a touchscreen then why not? Not exactly losing anything but you do gain some more functionality.