My view.. For what it's worth..
All these can be turned with normal wood turning chisels, however TCT ones work better.
PU- polyurathane, easy to turn and also takes a thread well.
PR- polyester Resin, more difficult to turn that PU, can be a little more brittle especially if the caster has overdone the activator. It doesn't take a thread well, however it can be threaded with care.
Corian - easier than any of the PU or PR blanks. Takes a thread well, however a little more sensitive.
Polymer clay - very similar to PR or turn, doesn't take a thread as the nature of the material is unsuitable
True Stone - easy to turn but can be very dusty, never tried to thread it so don't know about that one.
Ebonite - easy to turn, takes a thread easily. Doesn't smell very nice to turn.
Horn - similar to PR to turn, but stinks.never tried to thread it,
Antler - same as horn, stinks. Never tried to thread it.
Delrin - easy to turn, Takes a thread really well but doesn't like glue very much and some can resist it and not glue your tubes.
Non ferrous, usually need a TCT, they are allot more difficult to turn than any of the above on a wood turning lathe.
Aluminium- one of the easiest none ferrus materials to turn, however needs practice and speed needs to be right for free - hand turning. takes threads very well
Copper- same as Ali, but slightly harder.
Brass - same as copper but a little harder than copper or Ali.
Bronze. Same as brass but slightly harder..
Pewter, never turned it so don't know.
Lead - stay away from it..
There is all the many varieties of wood, very hard to the very soft and to the many different ones available from around the world.
I'm sure that the above list will disagree with some, but it's how I find them and I am sure I would have missed some that others on here will remind me or bring new ones to the list..
Look forward to the replies..