Get the Canon 600D. The 1100D is a really lightweight camera, and the extra lens (the 55-250mm) isn't very good - at least, not good enough to justify the lack of features of the 1100D.
The 600D has good performance and has some nice features such as 1080p recording in 30 and 24 fps, a fully articulating screen, and good ISO performance.
The 18-55mm is an equivalent focal length to the 18-55mm IS II, but the 18-55mm IS is "image stabilized" in-lens, meaning that if you have camera shake, the lens will eliminate it (to a certain extent). The II just means it's the second version of the lens made by Canon.
I really recommend that you learn more about photography, exposure, etc. before you invest in a big DSLR - it's a shame to buy a $500 camera and keep it on automatic all the time and not know what you're doing.