It's personal preference. I definitely wanted AWD (in my neck of the woods, no dealer within 100 miles had RWD anyway). I test drove both 18 & 19. I went with the 18"s because:
1) The car is my D/D and I drive a lot (23K miles since May 2 purchase). 18"'s have a more compliant ride on our notoriously lousy roads. And, I believe the 18"s are just as good a fit (if-not better ) than the 19"s for the true GT nature of the car.
2) The long term cost of tires. You can do proper rotations with the 18"s.
3) The OEM Pilot Sports are great for summer, but I knew I would have to buy a proper set of winter tires / have 'em on for c. 4 months/year. (I ended up buying winters anyway, because the Bridgestones suck in snow.) So happy I did. I plan on a better summer/performance tire once I replace the A/S's. Something for you to consider over there in Wisco.
4) I'm not going to track the car.
Now, I realize that I'm compromising a bit of handling performance, but not much. Also, I don't see much of a cosmetic difference 18 vs.19 n the OEM wheels. Again, it's personal pref/how you dirve/where you live. My $.02.