I've tried a lot of tires and it depends on what type of riding. For my situation I'm hooked on 170 Roads. I live on coast hwy 1 in California. I go out the door onto twisty canyons. If I'm going to work it is cool mornings. Pilot Roads warm up very quickly which is exactly what I need. It's a very modern tire.
I rode lots of 180s and always wondered why I was leaning very hard on the bar in a tight hairpin. At my local Duc shop I saw that a mechanic's track/street SS with numbers had a 170. He told me it is much better in twistys. I tried one and never looked back. I sold my 5.5 wheel and got a 4.5 which is better for a 170. Before I did I had a new 180 D208 on a 5.5 and a new 170 D208 on the 4.5 -- tried them both and for me it was very clear -- the 170 turns much quicker = fun. The 4.5/170 is something like 8 lbs lighter than the 5.5/180 -- guys pay a lot of money to loose that much weight from their rims!! I'm even thinking of trying a 160 P Road next.
I posted a question similar to yours several years ago on several lists and the general response was that 180s are sexier and 170s handle better. I do think that the 180s rule racing because they handle better with 100+ hp at a 100+ mph. That's where the big rubber comes into its own.
Guys kept saying the 180 was a 'chick magnet' but I don't think girls can even tell -- the 170 is not small. I think we'll have to go out and see which tire gets the most girls.
Al
96 SP Ohlins (fr & r) FCR 11:1