I wonder if I can draw on memory and maybe address some of the things WieWaldi (Vivaldi 😉 ) mentioned. What considerations were there?
(1) You want the bench to be stable, no wobbles, not become loose over time. (2) If adjustable, the mechanism should work well, and continue to work over a lot of years. (3) I chose hydraulic because cranking is tedious. I'd need to be doing a lot of experimenting on height because of the circumstance I found myself in. You also want control - not to "overshoot" the ups or downs.* (4) The surface you sit in. In the pic you see the old bench hardly had cushion - it was almost like sitting on wood. The new bench has both cushion and sufficient support. Where I was learning to lean from side to side, forward and back, without getting stiff, I found that this seat is just right. It gives just the right amount of support but also give. You also want it to stay that way over time. (5) The "lip" of the front of the seat - the subtle overall shape of the seat. Hidrau, meanwhile, has an ergonomic seat you can opt for.
My particular situation is that I was self-taught as a child years ago, and returned to piano decades later, so there are poor habits. I did not move at all - only my fingers did. I also had a posture of lordosis which I've worked to undo, so I'm hypersensitive to seating. Lordosis involves the hips, so your "seating area".
@WieWaldi , you referred to your office chair. By coincidence, I got a good office chair around the same time as a bench, and did research on that too. It was a toss-up between Steelcase (the brand you got), and the Herman Miller Embody which I ended up getting. I chose the "gaming chair" version. One of the considerations in the design was the ability to move in the chair, including a back that has a kind of mobile but supportive "spine" of its own. I've had a home office for decades, and I'm not getting younger. It was, in fact, interesting, looking at piano benches and then office chair in the same time period.
*footnote: Originally Andexinger had a problem for light weight people (under 110 lb.?) who had trouble getting it to descend, but I understand they fixed that
