You'll know best when youre trying them on but don't be afraid to try something different. When I tried on what im wearing these days for the first time I was like errrr I dunno, but ive actually received compliments about the frames. They dont make them anymore tho..not exactly, so I must treat them with CARE.
Anyway keep in mind that depending on your vision, smaller frames will force the use of smaller lenses which are generally thicker. However, technology these days pretty much lets you put some pretty powerful lenses into a thin small form. This usually costs extra. The pair im wearing right now cost me 500 cash a few years ago, but it was worth it to get the lenses thinned.