I know you weren't talking about the old car not working properly. That's why you shouldn't have brought it up at all. But since you chose to make the comparison, I ran with it. For many people, Magnas are no good because the gun doesn't work right with them installed, kind of like if a Jag XKE had a Jag factory-original milk crate installed where a seat is normally installed. It could be made to work, sort of, but the car deserves better. Jag, AFAIK, was never that stupid. S&W was, for years and years.
Pachmayr Presentations are a common manifestation of Roper design. They happen to be in rubber. Many other people make somewhat similar grips in wood. Hogue makes some very different designs in both rubber and wood. They are functional designs for many people.
If I am not mistaken, even you admit that Magnas don't work, that the gun moves in your hand, that you are very conscious of recoil. Welcome to the majority. I am simply pointing out that if a gun is for shooting, you are wrong in choosing Magnas. Of course, you may have a slightly different agenda, in which case you are probably right in choosing what you choose.
If you disagree with this, fine. Just remember that you are not the only who has a right to express his opinion; I do, too, and I just did.
BTW, none of this is intended to reflect on those folks, wherever you are, who actually find Magnas functional. I think that there are a few out there.