I'd buy pretty much any character from ANH over the Prequels, but in spite of what many people think, this isn't an either-or situation. Hot Toys is not holding back on a Death Star Trooper because they've released a Darth Maul, it just doesn't work like that. The Death Star Trooper is being held back simply because of the whims of the owners. They just don't feel like doing it right now (if at all) and they also know characters like Qui-Gon and Maul will sell more units and they'll be able to charge more for those characters.
It also may boggle the minds of OT fans like myself, but figures like Commander Cody will generate more buzz and sell better than the ANH Sandtrooper. A figure that I don't think did that great and therefore will not get the other ranks released.