The major differences between the 3i and 4i that really matter are the body being made in Japan, which is considered far superior to Taiwanese manufacture and the superior auto focus, which is functional in movie mode. Here is a link to my go to camera review site: http://www.dpreview.com/reviews/canoneos600d/19
The two cameras have almost identical reviews and you cant go wrong with either.
regarding the lenses, the 18-135mm lens was manufactured in part for improved video capture as you can probably tell from the list of features here:
EF-S 18-135mm f/3.5-5.6 IS STM – key features
Versatile 18-135mm zoom range – perfect for travel
Smooth, quiet STM focusing when shooting movies on compatible cameras
Dynamic Image Stabilizer for smooth movie footage
Fast autofocus with full-time manual override
Minimum focusing distance of 0.39m
It is a very nice over all lens with a a very good telephoto range and will give you plenty of picture taking options with out the need of a lens change. It also has an F-stop of 3.5 thru the range versus the 4.5 of the telephoto provided in the T3i kit. The two lens kit with the 3Ti gives you a bit more range in telephoto but are not as high quality as the single lens with the T4i kit.
IMHO, I would go with the T4i, for the better build and better overall lens and if I found I needed the extra telephoto range I would look at adding a larger range telephoto down the road. The extra $200 is worth it if you will be happier with the camera. Of course if you plan on using the camera for video at all, then the 4Ti kit is far superior to the T3i in that area and would definitely be the better choice. Last but not least, if you plan on ever upgrading the camera body, then your most important issues will be getting superior glass ( lenses ) because thats what youll be carrying over when you change camera bodies.
for cost comparison the EF-S 18-135mm f/3.5-5.6 IS STM goes for $481 on amazon just by itself. The 55-250 mm runs for just under $200 and the 18-55mm IS lens is also just under $200