What size swimsuit is the best fit for racing?
For a suit you intend to race in: Go to a swim store and try on different sizes until you find one that feels tight enough to be a bit uncomfortable. Then buy the next SMALLER size. For racing, you want the suit to feel really tight when dry. Nearly all suits expand a little when wet and stretch out a little after a few uses. You do NOT want little folds and wrinkles to develop, as these can cause significant drag.