I like every safe material I've tried and I suppose I will like the ones I haven't, when I get the chance. Cheap plastic feels great on my clit, glass can firmly stimulate my g-spot (suppose the same would be true of metal and wood) and silicone has a bit of give that makes penetration feel wonderful.
I haven't picked hard plastic in the survey because you said long term and I tend to drop hard plastic vibes and they crack around the base. I'm more careful with glass. I've also observed some discoloration on my PU coated vibe. Bleaching it only makes it worse.