I'd second what LeadPumper said - I don't see many guns on the line with the grip panel mount.
My first bullseye .45 was a Springfield with a frame mount similar to the picture. A Weigand (sp) I think. Worked out just fine.
When I bought a used Les Baer, it had a slide mount for the dot, and I found I liked it better. Not only does the dot sit lower, it changes the recoil by adding weight to the slide. I did, however, discover that the Bushnell Trophy dot I was using wasn't up to the task. Battery contacts shook loose after a while, luckily it wasn't at a match. A new Ultradot solved that problem, and it's been good to go.
If you get a chance, try shooting pistols with both types of mounts, see which fits you best.