I've owned 3 Ariens, all purchased used within the last 5 years.
One was an SS322 (938010) single-stage, I think late-90s. 22" width, 3hp 2-stroke Tecumseh. It was a good little thrower for small storms (3-4"), but when the snow got any deeper, I found it just got bogged down. Maybe the 5hp version, SS522, would do better, I don't know.
I also had an ST824 (924082), mid-90s. 24" width, 8hp flathead Tecumseh. It had a differential. It was a very solid machine, though it had clearly had a *lot* of use by the previous owner (I am guessing commercially). I used it for a few seasons, it performed very well. I love the differential feature, it made it much easier to manage than my previous solid-axle MTD 2-stage. With chains, I still had good traction, but turning was easy.
I now have a 1024 Pro (924120), from around 2000. 24" width, 10hp OHV Tecumseh. With a differential, headlight, and heated grips. I don't need a wide cut, but I was looking for a bunch of power, so I liked the 10hp/24" combo.
Unlike my ST824, this has the tall chute. I also added a homemade impeller kit. Perhaps from a combination of the two, the throwing distance is very good. The differential continues to be great. Though during some of the big storms this season, I've actually had to lock the differential, even with chains, to help drive into deep banks from the plows. The heated grips work very well.
I like the controls, with a simple crank to rotate the chute (it doesn't have the remote chute deflector). No finicky cables or "delicate" controls. Plus I can aim the chute exactly where I want, vs picking from 8 directions, or something similar. The only real wish that comes to mind is a slower forward speed for 1st gear, to let me inch into deep snowbanks.
This is my first full season on the 1024, but we have gotten over 100" of snow so far (close to a record for MA). It has been worked *hard*, and has performed very well. Some pics from the January blizzard are attached. The snow was 24" deep at this point, and the plows had left piles that were higher than the top of the chute (around 38-40"). It did very well.
I chose Ariens based on their reputation, as well as parts availability, and the support available online for the machines (a large, helpful user base). The availability of documentation from the Ariens site, including the service manuals, is a great feature. In my experience so far, the machines have earned their good reputation.