Day to day I wear glasses a lot of the time, simply because it's more comfortable for me than wearing contacts all the time. One thing I've noted in terms of when I'm wearing contacts on a night out though is that it is slightly easier to get and maintain eye contact when not wearing glasses. However, there are some quite fun bits and pieces that you can run with glasses on;
The photograph pose game - obviously there are lots of angles you can run when you have a camera/cameraphone, but when talking about the poses that really make an impact, one of the ones that never fails to get a laugh is 'The Superman'. Basically, you fix someone dead in the eye, then swiftly move your head toward them, and whip your glasses off, never breaking eye contact. Inevitably once you've shown it, your group will want to have a go at it.
Depending on your prescription, once you've started playing around with letting people try on your glasses, I quite like running the 'I want to know what you're like when you're drunk' angle. Get the girl to put on your glasses, look at the ground and jump (while still looking at the ground). My prescription isn't even that bad (I'm short sighted) but for anyone not used to wearing glasses, doing this will all of a sudden make them feel unsteady on their feet, and again provoke a laugh, which never hurts.
In general I would recommend doing whatever you're most comfortable with. Personally, I like the eye contact I can achieve when not wearing glasses, but when I've got them on, I don't let it hold me back.