Go for the Steadicam, I have the Smooth Shooter, the X-10 is a Smooth Shooter with an extra arm, I don't like my Smooth Shooter very much! It's great for cheap events however when you start going professional it's no good. The Glidecam 4000 Pro has quite a few design flaws that make it impossible to recommend, the gimbal handle is fixed and placed in a stupid place, the gimbal on the Steadicam can be moved up and down. When I try to get certain angles the gimbal on the Glidecam makes contact with the plate holding the camera, it's very annoying and a deal killer. You need an external monitor for good flying, the Steadicam has one standard as it should be. The Glidecam is only useful on a flat surface, when moving over rocky, bumpy terrain forget about smooth motion.

As soon as I can afford it, I'm selling my Glidecam for a Steadicam.