The T4i was replaced by the T5i -- so you'd have a tough time finding a new T4i (most dealers are long since sold out on that.) But there is almost no difference between a T4i and T5i.
You can currently get a fantastic deal on the 60D -- but that's because it has been replaced by the 70D. For the time being, Canon is still marketing the 60D -- but at a substantially reduced price.
On the 70D:
1) It has essentially the same focus system as the 7D -- which has 19 AF points and they are all "cross type". The 60D and T5i have 9 point AF, but all 9 points are "cross type".
2) It has Canon's new "dual pixel" AF -- this gives the camera the ability to do phase-detect auto-focus on the sensor (no camera has been able to do that before.) DSLR cameras normally do phase-detect auto-focus, but using separate focus sensors. When shooting video or using "live view" the cameras have to use "contrast detect" AF -- which is accurate... but slower and has to "hunt" for focus (due ot the nuances of the way phase-detect sensors work, they can not only tell when a subject is focused, they can tell which way they need to change focus to bring the image back into focus AND... they know how far they need to change focus. Phase-detect focus doesn't "hunt" for focus (assuming there is enough light.) So what this feature means to an end user is that the camera can do continuous focus while shooting video without focus-hunt and it works astonishingly well (better than any DSLR has ever been able to do... and actually by a fairly wide margin. Nothing else has anything like it.)
3) The 70D has built-in wifi. Canon makes apps for iOS and Android which can remotely control the camera and transfer images.
4) The 60D and 70D are both mid-level bodies... the control layout is a bit more like the pro bodies with a 2nd LCD display on the top of the camera, several instant-access buttons to commonly used features which a Rebel body would either equire use of menus or use of multiple-button pushes. They also add a 2nd dial -- on the rear of the body. When shooting in manual, the front dial controls shutter and the rear dial controls aperture. They are both positioned so that while looking through your camera, your index finger controls the front wheel and your thumb controls the back wheel and it's very comfortable to do. When shooting in a semi-auto or creative-zone mode, the rear dial handles exposure compensation.
5) The T5i and 70D both have touch-sensitive screens.
6) The 60D and 70D offer weather-sealed bodies. They are NOT waterproof (make no mistake about that). The weather-seals add gaskets to all body seams and o-rings on the dials to keep water and dust out of the camera body provided it's not under pressure (i.e. submerge the camera and it would leak). If you were _also_ using a weather-sealed lens (many of Canon's "L" series lenses are weather sealed, but you have to check each lens since not all models include weather sealing) then you wouldn't have to worry about using the camera in rain, snow, etc. Make sure you towel the camera dry before opening any doors or removing the lens.
You will notice quite a bump up in ISO performance (ability to shoot in lower light with higher ISO while maintianing low levels of "noise" in the image.) But you'll get that bump up in performance with all the bodies you are looking at.
Tim Campbell
5D III, 5D IV, 60Da
