Thank you for helping us by reporting bad content.
The Canon Rebel T3i takes the consumer level dSLR a couple steps closer to the mid-level Canon 60D with the addition of the rotating rear LCD screen, remote flash firing, and in-camera processing features. The already highly competent, older Rebel T2i already shared many important features with the 60D (and even features of the semi-pro 7D) including the 18 MP sensor, 63-zone exposure metering system, high ISO performance, HD movie capabilities, and Digic 4 image processor. With these new upgrades, it might make it even more difficult to choose between them. But there are some important differences.
If you are considering the Rebel T3i vs T2i, the Rebel T3i is replacing the T2i. Since both cameras share the same 18 megapixel sensor and Digic 4 processor, both the T2i and T3i will create images with exactly the same image quality, produce the same low light/ high ISO performance, shoot at 3.7 frames per second, and have nearly the same size and build quality. They are both offered with the same 18-55mm kit lens (with some minor cosmetic differences on the new T3i kit lens). The T3i is very slightly larger and heavier due to the addition of the rotating rear LCD monitor. And that is one of the biggest differences between the two cameras. Do you want and need a vari-angle rear screen or not? The other major difference is the ability of the T3i to remotely control multiple off-camera flashes. Like the 60D and 7D, you can use the built-in flash of the T3i to trigger other Canon Speedlites. Some other minor additions to the T3i include the Scene Intelligent Auto Mode, which is a feature borrowed from point and shoot cameras. When in Auto mode, the T3i will make a determination of what type of scene you are shooting - close-up, portrait, landscape, etc. - and automatically configure the camera settings accordingly. However, if you want to use a powerful and costly digital SLR as a point and shoot, you should probably save the money and just buy a nice, high quality point and shoot like the Canon S95. Other additional but not essential upgrades include the in-camera processing Creative Filters, and the ability to choose different image size ratios and to rate your images. (Helpful hint: press the Q Button while in image playback and you can access features like rating, rotating, and Creative Filters.) There is also a marginally helpful Feature Guide which gives brief descriptions of various settings and some additional video features like Video Snapshot, which you can use to shoot short video clips that are automatically joined together into a video, with music.