It is really annoying how everything is different from manufacturer to manufacturer, such that you can't really compare the brands. Salt vs. Frog. Footblaster vs. Motomassage. 1-2 large pumps vs. several smaller pumps. Specialized electrical panel vs. standard 50 amp breaker. Captain chairs vs. bench seating. Lighting packages, jet configurations, waterfall options, etc. Every brand has a special feature and every other brand has a comparable feature (with a different name, of course) that's either better for reason x or worse for reason y, depending on who you talk to. The only consensus I've had from dealers is (1) circulation pumps are generally a good thing (although I question how something running 24/7, even in the summer, is such a good thing ...); (2) built-in sound systems will eventually fail; and (3) everything they offer is far better than my old Costco spa. That's why its so important to find a good dealer you trust and select a spa that you'll be comfortable in.
You can't expect one manufacturer to call their features the same as another's. How could they pitch their system as superior?
OK, Joking aside now.
Most have some sort of Foot Blaster, they all work the same way. Personally, I'm not crazy about the Foot Blaster. In my Nevis, it doesn't take up space but other models from multiple manufacturers have Foot Domes which contain the Foot Blasters. Some people like them, some don't. My feelings are they are something to trip over and while provide intense massage, it's too intense for me. The Motomassage is unique to Hot Springs and has nothing to do with Foot Blasters. Motomassage is an in seat massage unit and seems like a useful option. There are many positive reviews on them. Personally, I don't know because the Hot Springs dealer I tried to visit blew me off. I don't know why my money wasn't as good as someone else's but whatever. Salt Vs Frog. Eh, both are proprietary systems, both are expensive to run and both provide proper sanitation. Some like the salt system, they say the water seems softer. They might be right. In short, both those systems do the same thing, at a greater cost than traditional methods, but at a greater convenience.
IMHO, circulation pumps are a good thing. 24/7 is a bit of a misnomer. They are available 24/7 but in actuality, only run when the heater is needed. More pumps are not necessarily better. In my tub, 4 seats are plumbed to the 6HP pump. It does deliver good performance and massage. One seat and the Foot Blaster is plumbed to the other, 3HP pump. Again, plenty of performance. The seat does have much larger jets for a deep massage. To me, the equipment is set up right. Others may not think so which is why wet testing is absolutely a necessity.
Get the best insulated tub you can find. Full Foam is preferred over any perimeter style insulation. A n acrylic over fiberglass shell that is self supporting would be high on my list, I believe all 3 brands you are looking at have both of these features.
Depending on what the dealer sells, they could be right. An Artesian, Caldera, Hot Springs and even the CalSpa are better built tubs than your old Cosco tub. Some other brands are not any better. I wouldn't replace your Costco tub with a Maxx, Vita, American Whirlpool, Master, etc. A good dealer, with an in house service department is crucial. However, YOU need to feel good about them. If you are uncomfortable with them, trust your gut and visit another dealer.