I like the 90 deg mount best. Sight sits closer to the slide. Mounting the mount to the frame isnt to bad once you get over drilling a hole in your gun. The instructions tell you to use a dremal and mill it out. The bushings you mount in the frame are shaped like a tombstone. I didnt trust my dremal skills so what i ended up doing was drilling a hole the same size as the as the barrel part of the bushing, heating it up and dropping it in the hole. Worked great. Once it cooled i just trimmed the plastic to clean it up around the bushing where it melted. Hope this makes sense.