I am trying for a "decades of arcade tech" approach. I definitely agree with the op that variety is key.

It would be great to have a rockola world's series for the 30s and something with unique flipper arrangements for late 40s. Then I would be covered up to 2020s.

Even though there are a few manufacturers in my collection, its pretty wild how they often comingle. My woodrail from the 50s is a Gottlieb but so is, as could be argued, my 1989 cocktail by International. The 1969 United shuffle bowler has alot of Williams stuff. Then there's the 20teens CGC version of a 90s Bally when they were at Williams.

I think even though the older titles don't have all the processing power of ss machines, they are challenging in their own right.