I have an Excalibur 9 tray and a cheap round one, I think made by Nesco.
The Excalibur is a much better machine. Its more efficient in terms of space and dries more evenly. The rectangular trays are easier to load and you don't have to have arts and crafts time to make liners for them. It's bigger and you don't really have the option of reducing its volume. With the circular stacking tray style you can use just the number of trays you need. You don't have the option with rectangular oven style dehydrators.