STi has more better stuff than just brakes lol
Depends what you want to do...
If you want to mod/tune and track it, then STi for sure...it's beast, and stock vs stock will be heaps faster than any wrx any day.
Sti has better drivetrain, suspension, links, control arms, etc etc, it's geared towards performance.
To get the handling of an STi in a wrx you will have to spend a fair bit on suspension/brakes, then add engine/drivetrain, and the list goes on....
If just daily the 2009 wrx is newer and has better features etc etc, you can still mod it to be beast but will cost you half your bum lol...
if you don't want to mod/tune etc then it is a newer/nicer car and would be the go....but I give you a month of seeing faster nicer looking/sounding/going wrxs around you and you will give in guaranteed
Remember most of the wrxs on the cruises are quite done up and beast!
edit: even though the STis are built with performance in mind, it's still very daily driveable...I'd go the STi