I really depends on what I am trying to do. I mainly do card magic vs cardistry. That being said, when doing magic I prefer bordered cards, they just looks so much cleaner in magic. If im doing gambling demonstrations, I would prefer borderless just because certain sleights and gambling techniques work better with borderless. As for cardistry, I feel like some borderless decks have their place, like virts, but I prefer borders in cardistry. Its nicer imo because in packet cuts you have really defined packets.