I would never buy a product from a company who posts this picture:
OMG! That is SUCH a rookie mistake: They are about to drop the skimmer lid.
OK - I may be kidding about
that, but I do like the Spa Dolly system. I was going to say "better," but I haven't used the Hauler, so can't compare other than by looking at the design in photos.
With the Spa Dolly, you can go off the back by tipping, and it is safe and stable when the tub is in the upright position because it uses a set of forks to hold things together until you are ready to pull them apart. The Spa Kart portion uses larger wheels, which can be mounted two ways for high or low ground clearance.
If you need to go off horizontally, you just take the tongue off, drop onto the little wheels at the front, and slide the spa off. Here's a video link to watch it in action, from the factory.
http://youtu.be/KPPzp3EjNgcThey have a winch if you need to pick up a spa horizontally, as well. Here's a video of that in action.
http://youtu.be/6Eq7bcf4D20Here's a vid showing the rear forks in action. Be aware: this shows the spa coming off the ground on blocks, but we almost always come off/go onto the Spa Kart. The forks actually have slots to slip into on the Kart, and once the spa is on the Kart, you simply pull the trailer forward to disengage from the Kart. Hope this is making sense.
http://youtu.be/cKaP56LI9aUI think they both look like systems designed by people who have moved a lot of spas.
OH! And be sure to get the "Spa Wedge." It's an inflatable lift bag, and it has saved my back many times over. My wife grabbed the little Orek canister vac which it shipped with to use around our home, so I found a cool shop vac built into a tool box which works great to lift and flatten the wedge as well as carry a few tools we commonly need on deliveries.
HTH