Seems simple; if you want better performance, get better tires, not bigger wheels. You're not going to see a measurable difference in performance from a very small sidewall height change, but you'll definitely notice a ride compromise on the 19s, and a subjective improvement in turn-in sharpness.
My Golf came with hideous 19s from the factory. I had new wheels and tires ready and waiting when the car arrived at the dealer. Put on aftermarket 18s that were much lighter, tires that were much better, and sold the factory boat anchors on eBay for very close to what it cost to get a GOOD set of wheels and tires. With a lighter wheel and tire package I ended up with a better ride, better performance, better handling, and better subjective looks!
The Aeros are fairly ugly but I think we'll probably go that route and possibly just ditch the covers.