A) Well basicaly what you miss out on if you buy express is that you dont get sculpture instrument or vintage instruments or a few other things like surround sound plus you dont get the other programs Logic studio comes with like mainstage, soundtrack pro 2, and waveburner and in logic studio you get like 18,000 loops and in express I think you get close to 5000 to see what you dont get compare both of what comes bundled with each and see which one fits you best at Apple.com/logicstudio and apple.com/logicexpress
B) Both can do the same exact things since theyre both logic, you can record midi,instruments use loops, rearrange tracks everything it really is an awesome program the difference is that logic studio comes with other seperate programs.
C) Both are the same program and logic is great for any genre! from dance/techno/trance to hip hop pop rnb heck you can compose an orchestra or make sum smooth jazz or country music anything is possible!
hope this helps