The price difference between 15a and 20a receptacles is minimal in the larger scope of things (I buy the better grade, not the cheap ones) and I prefer that 20 amp circuits have the 20 amp receptacles because it's a visual indicator that the circuit is the higher capacity which is nice in the situations where one might need to use a 20 amp circuit. Now in the house, that would primarily be the kitchen of course. But functionally, it's true that either one is going to "work".