It all depends honestly. The GTO is a sweet car to daily drive- comfortable, fast on the highway, etc. where the Evo is kind of boy-ricer looking. As for potential, yes- the LS2 has tons, but the Evo can run 11's for a hell of a lot less than the GTO can (unless you want nitrous which is fine- but I am talking 11's as-is, where-is kind of thing). There is a local guy with a high 700 whp evo that is daily driven (with the boost turned down on pump gas). Don't know what he runs, he is kind of quiet about it- but it is single digits

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If I were going for a quick car that with a few well placed mods is a brutal street car, I would probably go Evo. I wanted the GTO for the LS2 and comfort- against the advice of pretty much every one I know. They still tell me I was stupid for getting the car- they all say "nice daily driver, but too heavy, slow and IRS" lol. It depends on your goals. I wasn't looking for a drag car, just a fun, fast comfortable car. "nice daily driver" fits the GTO best, plus it isn't a common car and it has that aura of being a semi-collectable muscle car to it- drive it all week, clean it up and go to the car cruise night on Friday and get a bunch of oohs and ahhs

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If budget isn't an issue, get the GTO, build a stout motor for it and boost the snot out of it- you'll have a 700whp+ daily driver

. The only downside is the rear IMHO. There are parts out there to strengthen it, but they are retardly expensive compared to a solid axle rear and still not as strong once done. If I go much further power wise, once I start to break parts, I'll go solid axle before upgrading the IRS only to have "moderate" strength.
Overall- I don't know, tough call. Like I said, really depends on your goals.
Joe