How to decide which camera to buy

I want to have the option to compare the two cameras I'm looking at (Nikon d5100 and Canon t3i) side by side. What is a good place to do this? I went to Target, but they where weirdly tethered and sd cards were not in there so i could not take pictures for examples. Should I look at renting each for a day, or is there a store that will let me use each normally to compare?

There are a few places you can do this

1) http://www.dxomark.com/...nd2)/Canon
2) http://www.dpreview.com/...ikon_d5100
3) http://snapsort.com/...ikon-D5100
4) visit a proper camera shop and hold each in your hands

Lens where you will spend the most of your money but if you are looking for a package (kit) and you have no loyalty to either brand… See what your friends may have and ask them… That way you can share lenses if they are so inclined.
The lenses will determine what you can shoot without distortion (not sure what your main subject will be or your budget)… Both cameras are on the same playing field.