I've always wondered about the different types, but never tried anything else...
I don't play slide as much as I did in my younger days, but I have a bunch of different kinds...glass, steel, brass, ceramic....and in all kinds of different shapes, sizes, and thickness.
All in all...I lean toward glass, but as long as the fit is right, it doesn't matter so much to me.
Last year I was messing around with some slide guitar parts, and since it was so long since the last time I tried playing slide, I sat there and went through my entire collection, trying to see which one would feel the most comfortable for me.
I too tend to be stuck between using pinky or ring...like you say, sometimes one feels right, sometimes the other...which is why I have so many different style slides.
Anyway...I decided I would look for a slide that could easily work for both pinky and ring, and fit perfectly on both...which seemed like a tall order...but I came across these Silica Slides, hand blown glass, and uniquely made so that the glass is thicker at the top (almost twice as thick), which means it's tapered inside to follow the shape of your finger.
They have different sizes, and I found one size that when on my pinky, it fits perfectly down to the bottom of my pinky, but when on my ring finger, it fits perfectly down to my second knuckle, without sliding over it, so I can still flex that finger, and the slide isn't sticking way up above my finger.
I gotta say...these are the best fitting slides I've ever tried out. They're $19 each...but worth it, IMO.
Check 'em out if you are looking for something new to try:
Silica Sound
They will let you exchange the slides if you need a different size. I guesstimated two sizes that would be best for my fingers, then after I tried them, I returned one and got the second slide in the same size as the one I was keeping...that way I had a spare.
We have a mellow return policy.
For online orders, if your are unsatisfied with fit of your slide, we will exchange it for a different one free of charge. We ask that you get the slide back to us - this will help us determine where the fit isn't right. Use any shipping method you want. We will ship it back to you via USPS Priority Mail.
If you are unsatisfied with the slide, we ask that you return it to us. We will fully reimburse you, plus up to $5 for the shipping back to us.
In the rare case that your slide has a defect, take a pic or 2 and email them to us with a short description of the problem. If we determine the slide is defective, we will send a replacement free of charge.