I agree with David, these are three good companies with good products. Each company makes a high quality product and each stands behind their product. However, these companies and their swim spas are very different.
Here's one way to think about the differences.
Robert Lauter, CEO of Master Spas (Michael Phelps Swim Spa), studied political science in college. He has been working in the hot tub industry since 1979. Under his leadership, Master Spa purchased the technology from Exerswim which they branded as H2X, then later rebranded as Michael Phelps.
Everett Pearson and his son, Mark Pearson, of SwimEx are both engineers. They have a number of businesses that rely on engineering solutions to use composite materials for residential and commercial customers. They created SwimEx (which combines their knowledge of fiberglass with a unique swim current design) to serve the swimming and rehabilitation markets (with a focus on commercial customers, i.e. sports teams, pt centers, hospitals).
James Murdock, the president of Endless Pools studied engineering in college. He created Endless Pools to sell his modular swim spa to residential customers for swimming and fitness.
Taken another way:
- Master Spa has celebrity endorsements and trademarked features (swim number system, Wave Propulsion™ Technology, Xtreme Therapy Seat). Their swim spas have all the bells and whistles and look great out of the box.
- SwimEx was engineered for swimming and therapy. They have a novel construction and a unique current.
- Endless Pools was also designed for swimming and therapy. They focus on the quality of the swim current. They have one and two propeller models with different configurations and different current smoothing systems.
So for the bottom line, I have swum in a SwimEx. It has a great current that spans the width of the pool. And because the inlet it on the opposite site as the outlet, the current flows in only one direction. My advice, try it out for yourself.