I started playing back around 1991, and always used National brand thumbpicks (white or tortoise shell). They sounded great and didn't seem to wear down in a way that affected their tone or performance. Sometime in the last 10 years or so, it seems that National changed the plastic material they use in their thumbpicks, and (in my humble opinion) the new ones don't sound nearly as good. Do you notice a meaningful difference in the sound you get from different thumbpicks? And do you have any recommendations on which brand seems to deliver the best tone and don't seem to wear down poorly?