The main loss for B650 is that it officially doesn't have PCI-E 5.0 graphics, though some boards are being reported as working in PCI-E 5.0 mode, just not advertised with it.What would we be missing getting b650 instead of b850.
You may also need to do a BIOS update if fitting a 9000 series CPU, depending how old the stock is.
Personally, I'd say that B650 boards aren't worth it anymore, unless it is a really good deal.