Size
The Great Pyrenees is much larger: about 65 kg (143 lb) as an adult, against 29 kg (65 lb) for the Golden Retriever.
Lifespan
In UK vet records the Golden Retriever lives longer: a median of 13.2 years, against 10.9 for the Great Pyrenees.
Grooming
The Great Pyrenees needs more grooming, daily brushing, where the Golden Retriever needs brushing a few times a week.
Exercise
Plan for plenty of exercise with the Golden Retriever, and a modest amount with the Great Pyrenees.
Temperament
They differ most on independence (Golden Retriever: keen to work with you; Great Pyrenees: decides for itself) and on loyalty (Golden Retriever: friendly with everyone; Great Pyrenees: sticks close to its people).
Alike
Both are rated the same on prey drive: usually fine with small pets.