The only negative with paper tickets is if you lose them.

E-tickets can cause problems such as the time I was told that my reservation which was paid for was canceled mysteriously. They did get me on the flight but my seats were given away and I couldn't sit with my wife.

If there is a strike or canceled flight where the airline will need to put you on another airline's flight, a paper ticket is required as the other airline will be unable to accept the e-ticket.

I go with paper the majority of the time.