Oddly enough, I found myself working on two pianos of the same make and model, but different decades on two consecutive days. Yesterday it was two Boesendorfer 170s, 1952 and 1986, and today, two Baldwin Ls, 1964 and 1983.
Although the Baldwins spanned the change to Acu-Just hitch pins, the change in the Boeseys was greater. In that time-span, they had gone from a full perimeter plate bolted along the long side to the more conventional plate with no metal between the long side and the rib along the bass strings. As I recall, it has a Schwaender action, not Renner. I think I like the older one better, but perhaps I'm not objective about it. I've done a lot of work on it. It was damaged by a plumbing leak a few years ago.
The two Baldwins would probably be a lot closer to one another, but the older one is owned by a professional pianist who has worn it out several times over. It's on its second set of strings (maybe second-and a half--I was replacing a string today), third set of hammers, fourth set of key bushing felts, not to mention a number of backcheck leathers that have been replaced, stuff like that. When we have the chance to do a really good job on it, it's a pretty nice piano, but it should be serviced a lot more often than it is. The other one sees light use in an ordinary household. It could use more service too, but not nearly as much as the other. If I were to choose one of the four, it would probably be that one.