Numbers posted were for a stock, WRX STi.
Reg. WRX is posted at 227 hp, 5.5 sec 0-60.
WRX STi is posted at 300hp, 4.8 sec 0-60
Slalom speed 69.1 mph. Skidpad, .88g
BMW M5 is posted at 4.9 0-60 sec.
Slalom speed 64.7 mph. Skidpad, .90g
From
http://www.fast-autos.net/
The cars are so close, that it depends on the site. STi is posted at 4.7, 4.9, 4.8 sec, the M-5 4.8 or 4.9. Slalom speeds are close.
The STi is speed limited to 150 mph, though.
I believe that the Lancer Evo is slightly quicker than both cars.
However, the WRX STi WR1 (limited edition) comes in at 320 hp, and a 4.3 0-60 sec time.
Cheers,
D