I always do not like to use new cards, because they are very slippery, it makes my handling of a cards a little bit awkward (and I tried to fix it so many times, the same result) and they are kind of hard to control. New cards are only good for fans and some moves, such as the Push Through False Shuffle. Also, I do not like to handle old cards (I assume that you understand why). So, I like when the cards are in between those two conditions. By the way, it's really fun to watch some videos (including David Blaine's) where magician puts the deck on the table or in the spec's hands and they slide so bad because they are new, and it takes time to square them up and hold them together.