Which is better in your opinion?

A Canon - EOS Digital Rebel T3 12.2-Megapixel Digital SLR Camera
Or
Nikon - D3100 14.2-Megapixel Digital SLR Camera -
Or
Canon - EOS Digital Rebel T1i 15.1-Megapixel Digital SLR Camera

I would definitely choose nikon.

Since I'm a Canon guy I like the t1i. In fact I own one and it's excellent. Not the newest technology from Canon but right up there with the best consumer dslr cameras at this time.

The Canon T3 has yet to hit the markets, and it should, very very soon. It is the Canon Rebel Xs's replacement

the Nikon D3100 is the best camera up there, specwise, and can be compared to the Canon t1i. The D3100 is just a tad better.

best would be for YOU to go to a camera store and handle each camera for a good amount of time to see which one YOU like. You can't go wrong with either.

now what is cool with the Nikon is that it has autofocus while shooting video, whereas the Canon T1i does not