Depends how good you are on Poser. But the run down is! Gmod is really a sandbox game with a physical engine that happen to have decent posing capabilities for those who know how to utilize them.
Try Gmod if you will for the insane free amount of content is has. But for quality, Poser is your choice. It is a professional 3D platform, Gmod is not. It takes work and experience to get Gmod poses to look good. But there is hardly anything you can't do in Gmod. Pose, build cars, houses, a city, a plane and fly it. Or set of a nuclear bomb or unleash tornadoes on your hard work. That is just the tip of the iceberg.