I can't give you preference because I only own CS (and the 1st version of it might I add), but I can say that CS does "lock in" the what ever look you already have, as advertised. It also enhances gloss, though nothing substantial. The version i have is more a product geared towards durability then looks. After speaking to Sal, I feel (though I never asked him this directly) that the newer versions may do more in the way of looks.
UPGP and OS both are, from what I can tell (mind you I odn't own them) geared towards looks.