I apparently am the only one who finds one paddle holster conceals better than it's belt-looped counterpart: the Blackhawk Serpa. And before anyone gets into the "Serpas are dangerous" BS, I've used the Serpa for over ten years in duty situations, competition and training, and the Serpa is no more dangerous to use than any other holster I've ever used, and is easier to draw from.
That being said, for my body type, I find the paddle version of the holster conceals much better than using the belt-loop attachment. What I don't like is the new hooks they've attached to the paddle. I might as well wear a belt holster, as it's almost as hard to remove as a belt holster; I do have to undo the belt to get it off...but I do like the Serpa paddle holster, and it does conceal quite well under an unbuttoned shirt...
I started out with nothing and still have most of it.