Difference between Canon Rebel T3 and the T3i?

I just got really into photography and I've been borrowing my friends Rebel XT to do some work with and I'm ready to buy my own. I'm selling my Nook Tablet and my Canon SX30IS to see if i can make about $500 dollars (both in perfect shape and practically new). I can cover the rest of the cost for either the T3 or the T3i and I was wondering that if the T3i was even worth upgrading from the T3. If someone could let me know some Pros and Cons and Bang for Buck that would be fantastic. Also if anyone has any suggestions for a Nikon DSLR or something I would like to see how those compare to Canon too.

Besides the 12mp / 18mp difference in sensors on the t3 and t3i respectively and the articulated screen on the t3i along with the difference in video size - 720HD on the t3 and 1080HD on the t3i,
as a consumer you'll find very little difference.

The changes don't necessarily mean the t3i is better - different yes but in the hands of someone who knows how to properly operate both camera and lens, and as viewed on a computer screen, you'll notice no difference.

Since you're new to photography I'd suggest the t3.