I think there are benefits to both a workout buddy and a trainer. The trainer costs money and that sucks, but for some people that is motivation to get to the gym. A personal trainer is better than a workout buddy for beginners because they know routines you can follow and can assess if you are pushing yourself hard enough or coasting through a workout.

I think a workout buddy is better because there is more social connection. Once you've learned what you are doing and have a couple routines down then it might start to get a little boring and having a workout buddy there can keep it new and entertaining. A workout buddy will get you to workout during times when you might not want to or might or spontaneously ask if you want to go climb Mount Si. The thing about workout buddies is that they are not on your payroll and can't always make your workout time, so you have to be dedicated and committed and the buddy is the icing on the cake.

If I had to narrow it down, I would say beginners start off with a personal trainer at least for a month and meet people during the same time and at the same place that you workout at. Then slowly transition once you feel motivated and competent enough to do your own workouts.

What do you think: what would keep you working out longer and harder, a workout buddy or personal trainer?