Well, I've had friends with both GSs & Great Pyrenese, and I personally would not go with either of them. My friend who had the GS, her dog had a genetic disorder (I know...can happen with ANY breed), but it scared me away from them. The one with the great pyrenese, he is like the most obnoxious dog ever (second only to another friend's Weim). Anyway, if it were me, I'd be getting a golden retriever because of their laid back personality
If you are really set on a GS or a GP, I would go with the GS. Good luck