Really, the best way to test this is through just general playtesting against decks you expect to face. When you're scoring, ask yourself if it's enough to pay into an Ash trace to both keep the runner out as well as keep them off enough money to get in again. Against Faust anarchs, Ash is a harder sell, since D4v1d is getting them through larger ICE and just cards are getting them through the smaller ones. Caprice, though, you have to win psi games, and you want a server that is taxing enough that you don't have to win 3-4 in a row. Also, you're only getting 2 of them to Ash's 3, so you're going to see them less frequently.
So basically, play some games. Play a lot of em. In each situation, ask yourself if the other card would be better. Try and actually keep track of this, and then compare how many games and in what matchups each is best. Then pull the trigger and choose =)