Comfortable fit is what I wear, price is somewhat of an issue but I'll wear a $5 ultra cheap pair as long as they are polarized and fit good.
You have to remember that when it gets hot and muggy you will be sweating your boys off and you need a good pair that sits up off your nose so the sweat doesn't collect under the lenses next to your cheek bones. I look for the ones that have a comfortable nose piece, but as long as they are polarized they will work fine for spotting fish. I believe the pair I have now are FLW from Walmart? Can't remember since I've had them so long, but they are super light and work great. Be sure you don't scratch them up or you won't be able to see squat.