I don't think you can judge a WG by her nationality alone, but by how she provides good service, with a good attitude, and good personality.
You could see two WG's from the same country but be completely different from each other. One could be a right bitch, and the other good as gold. No two will ever be the same.
Sometimes it's down to us punters how we behave towards them. If we go in just looking for a pump and dump, they'll treat you like a dump. Go in with friendly attitude, they'll treat you kindly.
That's my experience and opinion anyway. Could be different for others.