I have used B square, Aim tech, and Redfield/ Weaver. Back in the day you couldnt look under the mount at the bead with the B square only aim tech.
All three are quality mounts. I prefer the aim tech, because it leaves a channel underneath so you can use your bead. I have a B square on my stoeger only beacuse it was the only brand that made a mount. You cant see the bead.
Aim tech also makes a rail that mounts to the rib of your gun. It looks pretty sweet to.