what one?: Which of these do you want? Which do you want?
whichever; any one that: Choose which appeals to you.
(used relatively in restrictive and nonrestrictive clauses to represent a specified antecedent): The book, which I read last night, was exciting. The socialism which Owen preached was unpalatable to many. The lawyer represented five families, of which the Costello family was the largest.
(used relatively in restrictive clauses having that as the antecedent): Damaged goods constituted part of that which was sold at the auction.
(used after a preposition to represent a specified antecedent): the horse on which I rode.