I was brought up on ivory keyboards. They always had a sure and luxurious feel. On the other hand, they need to be constantly washed. I used to clean my Steinway keyboard hundreds of times, it seemed. When I switched to Baldwin, it came with the more modern plastic keyboard. It is indeed more slippery, but hardly ever needs cleaning. Plus, I'd rather see the elephants left to live in peace, where they are becoming an endangered species! Here's one key difference (no pun intended) I've noticed. Over the years, an ivory keyboard would wear down, and sometimes develop very minute cracks along their length and sometimes nicks or chips along the outermost edge. The surfaces of some plastic keys instead seem to become pitted in the several notes around middle C which get the most intensive use. So that's another trade-off between the two.