997 GT3 benefits fm even lighter con-rods (more power, more responsive engine, more RPMs) & PASM (flexibility for daily use) compared w/996 GT3. on the other hand, there may be many folks trading up (fm 996 GT3) so you could probably pick one up at a good price.

on the matter of 'HP wars' - keep in mind it's not just how much HP or torque the engine produces, but how much of it is put down onto the road (a rear-engine layout does this much more efficiently). weight, grip & stopping ability are just as important as power.