I have both a Python and a 586, both blued and 6" barrels, and will never part with either one of them. The Python is more accurate and has a butter-smooth double-action, but will go out of time more easily if subjected to fast and hard double-action drills. The Smith is a bit more solid and almost as accurate, with a slightly more robust action. The S&W M27 is stronger than either, but bigger. I shoot mostly single-action plinking, and not very much per year. They are both fine revolvers, and it is fun to take them to the range together. Pythons don't show up too often in Alberta and go for a good price. P&D had a beauty a couple of weeks ago that sold for $850, about $200-250 more for a 586 in equivalent condition. Get them both! I have no experience with the GP100.