I own a 2009 Sedan as for looks (my opinion) i like it more but i find my self once or twice a month wishing i had the hatch. A quick grocery trip fills my trunk, can't put the kids bikes in it and i don't know how man times i go to the store and buy a boxed item that doesn't fit by 2-3 inches which would drop right in a hatch with room to spare. Get the hatch!
As for the STi vs WRX... they both put down similar numbers to the wheels on a dyno (+- 10hp/tq) the graphs below are from the same dyno, different year cars but they have the same engines.
WRX as you know is a 5 speed STi 6 speed. the WRX has a softer ride, STi has a beefier transmission and better suspension. The WRX is quicker in the 1/4 due to the 5 speed and slightly lighter weight, but once you add a turn the STi is gone.