Bassbob
Emissary
Utiliclip is more robust than the plastic clips, although I have some with the plastic clips and they have never failed me. The Utiliclip is more difficult to get off your belt so more suitable if you are very active and going to be laying down or like actually working and doing stuff. My first AIWB I bought with the Utiliclip, but all the subsequent ones I just went with the polymer clips. It's way easier to remove the entire holster and gun from your pants.Thanks - I just need to figure out what the heck a mono block + ulticlip would get me... and if that would be the way to go. I will definitely keep this in mind for my next carry gun. The jury is still out on whether it will be the new Mod.3, Walther PDP-F, or the Echelon - and I'd love to be able to EDC the Echelon, but it's definitely a size upgrade from my XD Mod.2 subcompact.
The mono block, I think, is a foam wedge that attaches at the muzzle end of the holster to tilt the grip back into your body and reduce printing. I tried them and the advantage was minimal. I definitely recommend the "Claw" though.
All that stuff is really for AIWB. If you're carrying strong side IWB I wouldn't bother with any of it and in my personal experience I would not use a full kydex holster. I would use a hybrid like the Crossbreed Tuck.