What are you planning on shooting? I've only used a couple of the cameras you've listed, but I can still tell you without hesitation they're all great picks for general use. Beyond that, it gets more complicated.
Imo, the Canons are very nice for video whereas Nikon's cameras are better for low light. Under ideal conditions both are fantastic. Nikons have better noise reduction so high ISOs are cleaner, sometimes at the cost of lost fine detail. The low end Canons have cheaper build quality and slightly worse optical finders, maybe, but build quality, optical finders, and frame rate are where cheaper cameras suffer in the first place; go one step up to a $1000 camera and you'll do a lot better with either brand in those regards... Image quality is awesome on the low end across the board.
I would say decide on the basis of which platform provides better lenses for your needs, but (with some exceptions) both platforms have great inexpensive lenses and the differences are more on the high end.
So I'd buy based on feel, unless you know what you want to do very specifically. I bought a t2i specifically for its superior video, but it's not a replacement video camera (you can't autofocus, for one, and skew means you can't shoot really telephoto without problems). That said, it has good video quality. I recently shot this with the kit lens, 55-250mm IS, and a few cheap ($200-ish) old nikkors:
http://vimeo.com/26129172
The resolution is less than my old hv30, but the "look" is better, imo. Good latitude, way more light sensitive, and I like that the sensor is the same size as super35mm film, so it feels a bit more "cinematic."