Basically I feel its a matter of opinion and what one wants. From what I've been regularly exposed to the malamute cross was more hard headed and broader bodied. However this animal typically had a wolfier phenotype than the German Shepherd cross which was more tractable. Some breeders have very strong preferences for one breed or another. Mals possess great size, smaller ears, bushier coats, are more stubborn than GSDs and are less inclined as a breed to be watchdogs.
Sibs are smaller, also possessing small ears and curly tails.
Some breeders do not like the blue eye color which can emerge, while others love this feature. Sibes rarely suffer hip dyslplasia, which plagues both GSDs and Mals. Some people have discussed shyness with GSDs. This developed, I believe when little attention was given, over many years to the quality of some dogs being bred, and shyness, or a tendency to fear bite developed with some Shepherds, as did a reputation for hip dysplasia. IF a GSD is out of a good line, with temperament and health given primary concern, these dogs can be a wonderful choice to use in a wolfdog breeding program.