18"s do look a bit sharper but for everyday use the 17"s have a better margin for error where curbs are concerned,not as harsh a ride and they won't brake the bank and you can put the money you save toward other mods. I just swapped out my 245/45/18s on my STI for 215/50/17 Hankook snow tires and while the change was a bit dramatic I kinda like a little more rubber around the rim and the beefy look works on the Subi.
I wouldn't have minded having 18"s but the 17"s work well and only spent $1200 on 'em. Sold my stock 16"s and tires for $800 so that really offset my cost.
