As someone else said, paper tickets aren't really paper. They are very durable. I can understand, however, why someone would want to have their tickets put on their key card if they are only using admission for that trip - it is easier to deal with everything on one card. If it's non-expiring admission that will be used again, I do think it's easier to have it as the original admission media simply because I have so many other room keys around (they seem to multiply, or maybe I have been too many times and save too much junk!!) that I'm always worried I'll mix up the wrong cards.