The breeds are incredibly alike in temperament. I am a dog groomer and schnauzers and wheatons are both very popular reeds that come into the shop. I always say that wheatons are just like big schnauzers. No other breeds consistently freak out when you try to pick them up lol.

Since they are so much alike I would say just get a purebred of one or both (but not to breed together). Breeding mixes is irrespnsible. Too many dogs in shelters -- people should be breeding to better a breed, not to create more.