I prefer loose stools.
[Ba dum bum - pshhhh]
Doh! lol
I prefer mine to swivel for many, many reasons. One is that when I turn, I want my stool to turn with me with no resistance. If it doesn't do that, then it becomes an obstacle and my playing suffers a little bit. I don't like having my mobility limited when I'm playing the drums. Another is, when I exit the drumset, I want the stool to turn with me so I can get out easier. At the practice studio, I am forced to bring my right leg between the snare and stool, and then stand up and go (and to do this, I must swivel). If the stool were locked, then it wouldn't spin, and it would make this more difficult. The room is small, so the wall is less than a foot behind me, but I am far enough away to lean back as far as I need to with room to spare so that I'm not confined.
But I think it's like an office chair. If I'm sitting in an office chair that doesn't swivel, then working on anything that isn't directly in front of me will become a little more difficult. Have you ever seen an office environment that wraps around the worker just as much as a typical drumset does a drummer? There are things slightly off to the left, and things slightly off to the right, and so a swiveling office chair is almost required to make things smooth. I can't imagine sitting at this desk and not having a swiveling office chair. It just wouldn't work. For one, I need to be able to swivel to get away from the desk. But for another thing, there are times when I go to open a drawer, and if the chair didn't swivel, then I'd feel a bit confined and restricted, and it would be uncomfortable.
So it is the same with me and my drum stool. Having it stationary is just uncomfortable and it feels unnatural. And this is huge for me because I want everything to be fluid and natural. Another reason why I prefer it to swivel is, if I need to make a very slight adjustment while playing, I can just swivel a couple of millimeters, and then I'm comfortable. But if the stool is stationary, then I either have to suffer until the end of the song and have my body aimed just a hair off, or I have to make my time suffer a little bit by lifting up off the stool a little so I can re-adjust so I'm aimed properly. And that brings me to what might be the biggest reason of all why I like my stool to swivel. I can swivel to be perfectly aimed at the drumset to basically reflect which part of the drums I am playing on, or to even reflect my reaction to the music! It's not that I have a wrap-around kit, or that I need to make huge turns, or that I want to spin in circles for show (lol wow can you imagine??), but not everything is directly in front, and very tiny adjustments can make huge differences. Plus, it helps me feel that much more relaxed. Nothing is fighting me, and that's important. I want the entire kit to work
with my body, not against it. And I want to stress the "entire" kit. Nothing should offer me resistance in that it doesn't work with me in a natural way. And I never knew this was important until I forgot to lock the stool down one day, and so I discovered on accident that this works better for me. This seemed to be fate, because it was during a time when I started trying very hard to relax my body while I play, and to approach the drums naturally so I don't have to force anything.
And also, I can sit on the stool facing away from the kit (like to my left), then lift my right leg and spin (so that the shin area can slip between the stool and snare), and then plant my feet on the pedals, and not have to lift and re-adjust my position in order to do this. Although, I usually just sit down facing the drums at first anyway. But there are times where I'll need to sit facing away first, and since I can swivel, I don't stand up turn, then sit back down just to face the drums.

It's kinda nice.
So, after seeing all of these benefits of a swiveling drum stool, now I know why some of my favorite drummers let their stool swivel. It allows me to feel more freedom than with a stationary stool, and it's a MUCH more relaxed feeling! I mean, it works
with me, not against me. And I guess that about sums it up right there.