Re: Tonal differences in slides?
My favorite is glass or ceramic. Glass has a great glide over the strings. Ceramic is similar, but your finger stays drier on the inside, since it's porous. Brass works good for electric guitar because it has a nice mellower tone on high notes. I've never really liked chrome steel slides, and they tend to be the brightest.
When I was playing a lot of slide guitar, I kept dropping slides on the ground, and the ceramic ones would always crack. The glass ones with the closed end, thin enough to fit on my pinky are my favorite......I think they're Bigheart Slides. I never liked using my ring finger, since I want that finger free to fret chords.