Either choice would be very good, they're both small enough so that the sidewall of the tire can make them virtually the same size. Low-pro's on the 15's can make it seem like a normal set of 14's.
However, Since i'm way more into performance, go with the 14's and a good set of tires. I'd say go with a 14x6 wheel and 205/55/14 tires. You'll get better cornering ability and possibly a better drag racing setup. DO NOT CHEAP ON THE TIRES!!!!!! Remember, if you drive aggresively (and i know you do
), the tires are the ONLY things holding you on the road!!!! My personal favorites are Falken Azenis, but since they are kinda expensive, my next favorite street tires are the Bridgestone Potenza's. Bridgestone just came out with a new tire series called Fuzion, Check em out, they should be cool and cheap.(They don't carry the Bridgestone name, but they are manufactured and warrantied by Bridgestone/Firestone)
Oh this is on my lowly lancer ES