Well I'm not looking for a perlino or cremello with purple feet, I'm talking about leg markings. I've definitely seen perlinos with white feet, and they stand out, and haven't seen many cremellos to start with, at least not in person, so I wouldn't be able to say, but I'm guessing it's as much a visual difference as "egg shell" and "white," which isn't huge, but is a difference. But, if they're bred to solid legged mares and throw a lot of "socked" foals from that pairing, they might have that gene in the soup.
Like I said, not that it's the most important thing, but if it's a difference between an outstanding foal with no white feet or an outstanding foal with 3 white feet, I'd go with no white.
To MacabreMikolaj, I'm stallion browsing, not mare shopping, but thanks for the input.