Put it this way, its all preference.
If you liked the WRX from its first ever debut, you'll love all the STi's etc... If you liked the Evo I, you'd follow the EVO's...
It is a close competition now, Because EVO's have so much publicity, the STi has felt in the shadows of the Evo..but STi have managed to make the STi very close to the E7 now.
The STi sounds more muscular with its exhaust and all...but the Evo VII is the quiet one that will sneak up on you. The STi doesnt have AYC and ACD does it?
Go EVO.