Reddit mentions of Hayward AXV621DAT Pool Vac A-Frame/Turbine Kit

Afraid I can't speak for the Dolphin since I've never worked with it. As for the others:

The Hayward functions well. It's an old design; tried and true. It'll climb walls and follow a pattern. Of the non-robotic cleaners you mentioned, it'll end up costing the most in maintenance. Nothing to break the bank, but it has gears, bearings, and feet that eventually wear down. If you're mechanically minded, they're not hard to break down and clean/rebuild. Maybe $50 a season starting in a year or two depending on the mileage.

(Aside: They've released a new cleaner that's meant to be a bit of a replacement that's worth looking at too. A bit sturdier and more modular. I liked the simplicity of working on it, what chances I got.)

Avoid the Smartpool. Sold these things and they can work very well. This might have changed, but as of last year you don't get a warranty if you buy online. And it's just about useless without that. I'd say 30% of the ones we put into the market came back within the year with some issue. The first gen had cord issues that they corrected. WITH the warranty we'd have a free replacement part, tune up, and test, and you'd be back in business within a few days. Without a warranty, you're SOL. Get it in store or don't get it at all.

For the Baracuda and Kreepy, you'll be getting one of the simplest, no BS cleaner types on the market. For wear and tear, they've got a diaphragm and the foot pad. Easy day. However, that mechanical simplicity also means they function simply. They might not climb the walls, depending on pressure/slope/depth. They'll also be random in their pattern. Not uncommon to have them loitering in certain areas.

The BIGGEST thing I can say about any cleaner you get, it's not a 100% set and forget solution. Take care of it! If you're going out of town, by all means leave it in the pool on a timer. It's great to come back to sparkling water; that's the whole point of a cleaner!

Don't, however, leave it in 24/7 exposed to the sun and chemicals. I've seen three year old Hayward Navigators that looked like they'd been drug through a minefield with repair costs higher than buying a new one. I've also seen Navigators that were over a decade old, bleached white, but still trucking with the occasional part replacement. Like a lawnmower, you've got to hose it off occasionally, check the insides, and keep it stored when not in use. If you do that, your $500 will go a long, long way.