I also was in a similar situation last year. I had been accepted to work(read: intern) at a large summer theatre festival, albiet with no pay. It would have been great for the networking alone, if there hadn't been this other job on the horizon. I received an offer for this first position the day before I interviewed for a position with a local new plays festival. Now, this job, while less prestigous, paid very well and I have a strong interest in new work. This interview went extremely well, perhaps the most comfortable interview I have ever had, but then I waited. I waited for over a week, putting off the large festival (I made it a point not to answer my phone...which may have not been a great move, but it kept me from lying to anyone point blank). I finally got in touch with one of the women I had interviewed with for the second job, the artistic director, and explained that while they were my first choice, I had another offer that I really needed to address one way or another. She emailed me back within an hour and said not to take that job, that the production manager would be in touch with me. He emailed me an offer within the next hour. I accepted the position with the group I really wanted to work with, and thoroughly enjoyed myself, and will be returning this summer. Sometimes it really pays off to play one group off another group, to show the interest that other see in you.