Actually, Perry's are not that much bigger than Foundry's. On the other hand, Foundry's have are slightly clunkier, less... I don't know... proportioned. Perry new Afghans are more anatomically correct. It is odd, as they can serve as a case study of how artists evolve their styles with time -Foundry Afghans were also sculpted by the Twins-. I wouldn't put them in the same unit, but they can be in the same army without being too noticeable, once painted and based.