The hatchback is stiffer and thus handles better. It also has more cargo room. If you want better handling and more cargo room, get the hatch. If you want to look like a dweeb, get a sedan.
Disclaimer: I am biased.
2012 Focus SE Hatch 5spd sport package, Tuxedo Black Metallic
Road Magnet springs, custom CAI in the works, and fuzzy dice on the mirror