1) I personally try to collect all variants of a particular chip.
2) Try to get the best chip that I can but I am not opposed to a chip that shows some wear from being on the tables in my collection. There are some chips out there where a worn chip is going to be as good as it gets and I am not opposed to having a chip like that in my collection either. I kind of like the history that goes with it, cigarette burns are kind of cool...