I've bought this brand and style for a while now, of all the BBs I've tried, this one just seems to be the most comfortable.  The elsatic strap doesn't feel too tight or leave that annoying red mark around your waist, and the soft material is easy on your thighs and package.  Like with any clothes, you're probably just going to have to find a brand and style that works with you... but for me, this particular one works the best.  (the ones with the white strap, though nice, do not fit as well as the elastic band tends to fold over on itself whereas these do not)

There are a lot that I also like (Puma, Dockers) that are good for the price... I can't really justify spending a lot of money on undergarments that, quite frankly, nobody is going to see :(