To me retention adds bulk (usually) making concealment harder. Police need the retention due to open carry, close proximity to crowds and "bad" guys, having to chase (running) after said BGs to arrest them. They may have to get into hand to hand with BGs.
I want to surprise my advisarry (sp), deploy my weapon, avoid mixing it up with the BG. I don't want levers, snaps, buckles, failing or hanging up on my cover cloths.
The only retention outside of proper holster to gun fit would be a screw tension option (tightens fit).
That why I chose deployment.. Just my opinion nothing more.