i have used acrylic, wood, micarta, and have a few in ivory. i like ivory best 4 the looks. micarta is my favorite 4 every other reason. wood properly sealed does work well, acrylic works well too. it is just a personal taste thing 4 everyone i think.
I do not think there is any best material. While I like Ivory, if all my razors were scaled in it I truthfully would find it boring. A razor's scales adds just as much character to the razor as the blade itself. Much of this is personal preference, but I feel that the scales and material should compliment the blade, be it acrylic, horn, ivory, wood, or carbon fiber
I like simple hard woods (walnut, mahogany, oak) although I also have some really nice but rarer woods. Ivory, plastic, bone, etc are all nice and provide variety but the wood just gives me a comfortable feeling. I have a 7 day set of Clauss razors that are done in plastic/celluloid and I'm seriously considering re-scaling all of them. Longevity isn't a problem with most of the materials that are used if you take care of them. I can imagine some issues that could be repaired on wood that couldn't be effected with ivory or bone or plastic or ... but the truth is, I haven't run into those issues in the wild. If they are good when I get them, they pretty much stay good.
So far I got 2 in desert ironwood, one in ebony wood and one in ram horn (denser harder and more durable than caw/buffalo horn which I do not like). I paln to get ivory and one in G10 or micarta.
Don't own any ivory yet, but i would say it is my favorite for appearance. Favorite I own is G10 in ghost jade. Zero maintence, nice weight and looks pretty nice too
I like the practicality of ivory. Its strong,weather resistant,dirt resistant,hides scratches ,each piece is unique,very easy to maintain,and very easy to work with. I also like horn and don't mind acrylic or bone. Micarta and G10 are ok but I do not want to be the one working it.
I am partial to inorganics like stainless, lexan, plexiglass, resin, aluminum, acrylic, etc. On my last ship I salvaged some stainless steel from a door that I replaced, and I will eventually make some GD scales out of that. With metal it is a good idea to use an inner liner of a plastic type material.
Wood can be pretty, and I am partial to ebony. Someday I will probably try sandwiching ebony and maple veneers in epoxy for scale material. I have mostly avoided wood but not entirely.