I'm typing this right now from my Model M... I don't know that the material itself makes a huge difference, but this well used M still has some of the texture left on its original PBT keycaps, while I managed to get a little bit of shine on a new set of black Cherry ABS doubleshots in only a year or so of use. (I'm also that guy that machinists hate because apparently my natural oils cause steel to rust if I pick up a part with my bare hands and not a shop rag, but I digress.) So, long story short, if PBT is molded with a texture that your fingers like, it will maintain that texture better long-term and therefore when used for a while, will feel pretty much the same as when new, while sooner or later ABS will always feel a little slick and greasy because your hands will be ever so slightly sweaty and the texture of the ABS caps will have worn off, at least on the ones that you regularly use to type. That said the Cherry PBTs seem to have little texture to begin with (or the ones that I have were really hammered on) but still don't feel as slick as ABS, so maybe the material does contribute at least a little bit to the feel.