I've been pondering this for a little bit. The latest exhaust "clarification" certainly hasn't helped my resolve w/ STX.
I know that the 2.0 WRX w/o question is more competitive in STX than ESP, but a national championship has never been a realistic goal for me anyways (I'm a decent driver, don't think I'll ever be a great driver ). I think an adequately prepped WRX could hold it's own in ESP in regional/divisional competition.
ESP lets you skip any "worry" over boost and exhaust. Suspension setup would be very similar. I currently have two sets of autox rims, clearly that would still be a necessity as R compounds are a given.
SP also has a up/back date clause- so any year (wagon/sedan) bits are fair game (thinking wider track up front possibly).
SP tires are expensive (not that ST tires are cheap mind you).
With a wagon I know that 275's aren't in my future, but 245 or even 255 would be doable.
For "summer" daily driving I'd probably run basically what I am now (decently treaded hi po street tire on 8" rims). I'd want to go a little wider for competition, what's accelerating this discussion know is i think I found a nice set of SP rims, so it's time to fish or cut bait