I agree. But, by the time they ceased production...
Both nameplates were really not much more than rehashed versions of some other car GM was making. There were no longer unique engines and drivetrains which once made a difference. As far as the designs go, you can look as far back as you like and see that except for grilles and taillights, many of GM's offerings were just variations on a central theme. No that I didn't like them. I did! But the more I look at offerings from the Big Three in the fifties and sixties, the more I see that they were all badge engineering most of their models.That philosophy came home to roost in the eighties and nineties as the manufacturers tried to streamline production. Eventually, there was really no reason to make Mercuries, Plymouths, Oldsmobiles and Pontiacs. I loved the Pontiacs and Oldsmobiles of the sixties. But from the mid-seventies on, Bruce is spot on.