Size
The Norwegian Elkhound is a little larger on average: about 22 kg (47 lb) as an adult, against 18 kg (40 lb) for the Keeshond.
Grooming
The Keeshond needs more grooming, daily brushing, where the Norwegian Elkhound needs brushing a few times a week.
Exercise
Plan for plenty of exercise with the Norwegian Elkhound, and a moderate amount with the Keeshond.
Temperament
They differ most on independence (Keeshond: keen to work with you; Norwegian Elkhound: decides for itself) and on handler demand (Keeshond: suits a first-time owner; Norwegian Elkhound: needs an experienced owner).
Alike
Both are rated the same on voice: very vocal.