You can't really decide on which one to choose just because, there has been the great Canon Nikon debate going on forever now. Your best bet would be to someplace that sells both and hold them in your hand. Whichever one feels the best in your hand, get it. It is sort of like buying a pair of shoes, comfort is very important. I am typing this in a hotel room after holding my Canon XTi in my hand for the last 7 hours, shooting over 800 pictures at a wedding. Do your reasearch and hold the actual cameras, you will come to a conclusion.
I am off to bed, dead on my feet tonight...