Not sure about that specific brand, but I know of 2 installations using the EXZ-Pad, and after 4 full years in MN, they are still going strong. But the people who installed theses put them down on a prepared base, not directly on the sod.
Check to see that for any spa that you consider purchasing it's ok to use that type of base. Damage to the shell due to an insufficient base won't be covered in your warranty.
It's very important to level the base as much as possible so it fully supports the entire spa.
Some spas advertise that they can be used without a foundation, and others may insist on the concrete base.