Neither. I love traveling alone because I can do as I please, when I please, most of the time. Still, having a fun companion is also enjoyable. Once when I was with my ex-boyfriend on a long car trip, we got on each other’s nerves and stopped at a small amusement park where we bashed each other with bumper cars. We felt much better after.
Also, in airports when you have a delay, it is not fun to listen to another person bitch and moan when there is nothing I can do to change it. If I am alone, I can take a bump for a free flight later.