So, snaps will do almost as good as loops?
I have no first hand experience with them, but I think they would. The Alessi CQC-S (and Ritchie CQ-QR), Sparks Axiom, Rosen Premier, etc., are all quite popular holsters and I can't think of any review where the reviewer commented the design was significantly worse for concealment than a similar design with loops.
Conversely, I've not seen many claim a paddle holster as a good concealment option (Kramer's MSP as the lone exception).
One of the key features of a good concealment holster is a trailing loop (or snap attachment) that pulls the grip of the gun close to the body. I can't think of a paddle holster with that feature, but nearly all of the snap attachment holsters have that feature.
In the loops vs snap attachment holsters, as a for instance, using Lobo Gun Leather as an example maker, taking it to somewhat of an extreme, would be the Lobo Combat Classic (
http://www.lobogunleathers.com/lobo_combat_classic ), which is a loop holster and their 1-SL Pancake, Snap-Loop (
http://www.lobogunleathers.com/1-sl_pancake_snap-loop ) which is a snap attachment holster.
The Combat Classic, while having a loop, doesn't have a trailing loop to pull the grip of the gun towards the body. The holster could be concealed, but the focus of the holster is probably more geared toward range/training/competition use. The 1-SL Pancake Snap-Loop, while a snap on holster, does have the trailing loop that will pull the grip to the body. This holster is better designed for concealment than the Combat Classic even though the Combat Classic is a loop holster.
However, if you were to call Lobo, I suspect they'd still recommend their Enhanced Pancake (
http://www.lobogunleathers.com/enhanced_pancake_model ) as their most concealable OWB holster. It's just degrees of concealment.