Remember the old Steven Wright joke, "My socks DO match. They're the same thickness."?
This sort of describes me when I choose discs. I won't want to throw a GStar Teebird along with my Star Teebirds, because GStar does not feel the same to me. And, K3 Kaxes do not feel the same as K1 Kaxes do, in my opinion.
Much of the time, if given a choice of throwing the same mold in different plastics or throwing different molds in the same plastic, I will choose to go with multiple molds in the same plastic. And, the plastic does not necessarily have to be exactly the same for all the molds. There can be multiple plastics; but they should feel the same. There is a tactile sensation from each plastic. For some reason it is important to me that every fairway driver have the same grip in my hand. It's okay if one of the discs has a somewhat larger wing than the others, as long as it grips the same as the others.
So, when someone would say that Philo sometimes uses Champion Rocs, I would think, "Oh, but those are nothing like DX Rocs. It won't feel the same."
I think that a person who loves some particular plastic might be inclined, as I am, to use discs that have the same feel as that plastic. And, newer players like me who have had premium plastic available from day one, while perhaps having less experience with base plastics, may not be inclined to try many base plastic models because these are not what we learned on. The base plastic doesn't feel the same. And, as others have stated, those who use premium plastic are probably more inclined to use a greater number of molds due to the difficulty of beating in premium plastic.