I buy suits that feel comfortable, but since I don't like the cut of most of the bottoms, I always buy a pair of swim shorts to wear over them. Everything is covered that I want covered, and they rinse out easily and dry quickly like the suits.
DD#1 is a larger gal, and she buys the same way as I do. She likes the option of having the shorts to wear at some public places, but at friends she is comfortable just wearing the suit.