Is a three wheel dolly better than a four wheel SpiderTrax dolly? It's definitely more difficult for the average DIY'er to tackle, and unless you have clear markings on the wheels, setting the rotation can be a bit tricky. There's one thing that a three wheel dolly can do that a four wheel can't, and that's rotate in 360 degrees without changing the center axis. Not super helpful as a camera movement since you can already do that with a basic Fluid Head, but if you place a stage and a product, you'll have yourself a nice 'lazy susan' style rotating table. Outside of that party trick movements are pretty much the same. Here's another version of a three wheeled rotating camera dolly (technically 6 wheels) by the same guys who make the iPad Prompter on 15mm Rails, and looks like a pretty solid build.