The dev said it's the exact same game with no benefits at all on the PS5. Same loading speeds, graphics, and so on. Nothing at all unique to that experience. So, the main reasons to spend the extra $10 is the PS5 box (if you collect PS5 specific releases) and possibly having a separate (but same) trophy list.
Echoing this point but also I heard the PS4 disc was confirmed to have the PS5 Upgrade available via store for free ; so even IF you wanted to play the ps5 version you could with the PS4 copy. Really the PS5 collection point is the only thing I can think of now.
I searched on some other PSN profile forums and research as I just purchased the PS4 copy myself for $20 too.
So there's been nooooo deal for RE Village GOLD yet - right? I was holding out hope but as more and more ads leak its looking bleak.