I agree with shroomgirl that bouncing around is not good for resumes, but you can learn so many different things from different chefs. This is what I do to help that. The job I am at now, I have been at for over five years and started as a breakfast cook and moved my way up to sous chef. The shortest period of time I've been at a job, not counting part time extra income jobs, is three years. About 2 years ago when I wanted to move out of a line cook position into a leadership roll, the hotel I am currently working at told me they had no position for me to move up to. That meant it was time for me to look elsewhere. I printed out my resume, it wasn't very long because I was only 23 and like I said the shortest peiod of time i stayed with a job was three years, but with in a week I had a job as the banquet chef at a different hotel. They told me the reason the hired me so quikly was the length of all my previous employment. I gave my current job a two weeks notice, but also told them that I would stay on part time on an on-call basis. Those two weeks were very long because I was working both jobs practically full time. The day after my last day of my two weeks notice, the first job fired the executive chef, promoted th sous chef, and called me offering the sous chef postition. I did immediately tell the new job but told them I had not made up my mind. The first job said they would keep the postion open for me until I made up my mind as long as I was there helping the now over worked exec. chef, the new job offered me more money. What to do. So I exhausted myself and worked both for six months until I made up my mind. I could have made a little more money at the second job but I just didn't feel it. I was strictly banquets there and if the catering director didn't book parties (like she did for the entire month of Feb. because she was too involved in NACE) I would end up doing things like serving continental breakfast for the hotel. Probably the highest paid continental breakfast server in the city, but not what I wanted to be doing. So I gave them a months notice. They of course offered me more money but I appologized and turned them down and told them that the money wasn't an issue. Business, staff (or lack there of at the second job), travel time, and learning experience meant so much more. So I went back to the first job for a little less money, 10 times more work, and 100 times more satisfaction. Because I never left payroll I didn't have to start over with vacation and benefits and the length of stay is that much longer on my resume.
So my advice if you made it through my long winded story, pick the job that will satisfy you the most for your needs, stick with it but if you have the urge to jump around do it part time while you still keep the first job. If and when you leave any job don't burn any bridges, you may need to go back over them.
P.S. Also in agreement with shroomgirl pick the one you would like to spend 12+ hours a day at. I don't have the time to take on a part time job any more even if I wanted to.