the GTPs are going to be faster that the GTs. rated for 40 hp >. but with the blower on there you have more potential for modding it. you can make a GTP fairly quick for cheap. in order for the same performance out of a gt youd prolly be looking into some type of forced induction, depending on how fast you want to go. the most common being the top swap. with a top swap ( gtp top end on Gt lower end) youre running a higher compression that a GTP, making the TS'ed GT faster... but also more problematic and prone to detonation
they arent like imprezas, evos, or srt-4s. those cars are (practicly) always beat on. GTPs on the other hand are owned by a broader spectrum of people. you could find one that has been beat to absolute dust by the highschool kid who thinks its a race car. on the other hand however you could find just as many that are owned by old ladys that drive it once a week never bring it over 3 grand and have all service done by the dealer on time.
hope this helps, good luck