I like the RAM, but haven't tried any of the others. I bought the RAM because I liked (and still do, it works great) the swiveling cup holder. You can move things around pretty easily with the RAM system and they have a million different gizmos available.
My mount wasn't in the poll, but I chose the "Space Station" mount made by Ed Sets. I wanted my GPS to be in the center of the cockpit and not block any of the bikes instrumentation. I wanted to be able to easily hide the wires for the GPS. I wanted the GPS to be close to the rider so it would be easy to see and operate while riding, and I wanted the GPS to be vibration free with no bouncing. The Spacestation mount has met my needs perfectly.
I use the RAM for several reasons. It keeps the unit secure. If you switch from one brand of GPS (or whatever) to another, all you need to buy is the new low-cost cradle, about $10. Absolutely no vibration, not only on the GW but also on my Harley and my two ATV's. Easy on - easy off. Sturdy, only broke one piece in 4 years of using it on an ATV, where I was constantly taking it on and off for various reasons. Two emails had me a new one in a few days, free of any cost. One email to let them know what happened, another with a digital photo of the broken piece, which was a cradle for a Magellan GPS.