I think it depends on your climate. A hat that barely covers the ears is probably okay for an evening stroll on a California beach. But here in the Frozen Tundra where it gets 40 below zero, we need a hat that covers the ears. I have a 22 1/2 inch head and mine are 8-9 inches in length. The 9 is about an inch below my ears and more like a bucket hat.
Welsh corgis are cool.