What is difference between T3i & T3?

[MikeSowsun]

The T3i is better value for most people. The T3 is basically a stripped down T3i with fewer features and a slightly lower price. 

Another important consideration is that the T3 is sometimes bundled with a basic 18-55mm  "Kit lens" that does not have Image Stabilization while the T3i always comes with the 18-55mm IS (with Image Stabilization)  

Some of the main differences:

12 vs 18 megapixels

3 vs 3.7 frames per second

2.7" low-resolution  fixed LCD screen vs 3" high-resolution flip out LCD screen

9.2m vs 13m flash range

No option for wireless off-camera flash 

Fewer video recording options

No external microphone jack

No self-cleaning image sensor

[TCampbell]

Within the Rebel line, Canon traditiona maintains a low-end model intended to be the most affordable DSLR in the lineup.  Each year (more or less) then tend to introduce a new model intended to be the top of the entry-range.  

Last year, for example, they introduced the T5i.  The year before it was the T4i.  And the year before that it was the T3i.  (They have not made any announcement for a new model this year -- at least not yet.)

Keep in mind that this is what the T3 is... the most affordable of the entry bodies.  The differences between a T3 and T3i are huge -- it's not like the "i" suffix version is the same camera with a few features added... they really are completely different cameras.

Above this whole entry range (all the "Rebel" bodies), there are mid-range and high end bodies as well.  

The progression of bodies is roughly:

T3 -> T3i -> T5i -> 60D -> 70D -> 7D -> 6D -> 5D III -> 1D X

With the left side being most basic and most affordable.  The right end of that list being the flagship and highest end (but most expensive) models.

Some bodies are optimized for specific uses... The 70D is optimized for video.  The 7D is optimized for action.  There's a 60Da (which I didnt include on purpose) which is so highly specialized that it's intended only for astrophotography.  The 6D and up are all "full frame" bodies -- so it's not fair to say a 6D is "better" than a 7D because the two cameras are designed with somewhat different purposes in mind.

[htxcameron]

which camera is best not price wise

[ebiggs1]

Of those two choices, the T3i.  But the best Rebel is the T6i.

This is a very old post and the T3/T3i has been discontinued.  It is replaced by the T5i/T5.

[Waddizzle]

The best Rebel is the T6s, IMHO.  The additional features over the T6i make it more than worth the cost difference.