I would argue that paying the little extra money for the T4i is completely worth it. It has a newer faster processor and a new touch screen that makes navigating the controls a breeze! I owned the T2i for two years and upgraded to the T4i and it has been fantastic. It's important to get a good lens to really show what your camera can do. I recommend the Tamron 28-75 2.8 lens. It's an overall pretty awesome lens. that's just a side note though. Hope this helps!
This Camera is in class kind of the middle of the road for the top end of Canon, BUT! I have had really good quality pictures with this camera. The movies have be very good also. Keep in mind that a camera is just a camera with out the right lens or settings for each shot.
But if you don't have a lot of money to spend on a camera then the Canon T4i should work for you well... Go to my site and view my photography work. This will give you and idea on what kind of photography you will be turning out with this camera... You be the judge. https://www.facebook.com/PhotoByJamesPhotograohy?ref=hl
I wish I could help you there, I don't do much video recording on my camera. I've never tried to use any programs for video. But usually canon has a software that comes with the camera on the disk that allows for video and picture conversions.
I have not used a 60D, but I bought T4i this summer and I am thrilled with the results. It is 1000% better than the Rebel XT. Sharper image, better color rendering, etc. I could not be happier with the performance of the T4i.
Yes. Canon does their best to make all their EOS cameras use the same lenses. Some features on new lenses (like the continuous AF of the STM lenses) won't work on the older bodies, but the lens will fit and work like any other lens you've used with single shot AF.