Stock for stock, an Evo X will eat up an STi in almost every quantitative performance test (and most qualitative ones too). I came off an '08 Evo X MR (had it for 3 years) into my E90 M3 and they are worlds apart. I say test drive all 3 back to back (same day) then make your decision.
If you can "easily" afford an M3, then get one and slap on an ESS blower kit... you'll never have to look over your shoulder for 99.999% of the STis behind you.
SUPER RARE 2011 E90 6MT ZCP SLICKTOP FOR SALE!!