Well, I'm 18, and I usually date guys who are 2-3 years older than me, but I would said that it's too much to wear a suit on a bar. That makes me the impression that the guy is too old for me (because I think he works and doesn't study anymore)
suits are always sexy, but even sexier when he's actually wearing it appropriately. Weird to see a guy partying it up in one - unless it's like a really fancy club / bar type place where great dress etiquette is required.
I like the shirts worn under the suite better though, like when the guy takes off the top jacket of it.
I've not seen one man who doesn't look absolutely delicious in those collared shirts.