If I had to choose between a nurse with 10 years of daily dermal filler experience and a doctor with 1 year experience, I'd probably go for the more-experienced choice.
That said, in most cases, a doctor is usually going to have more training and more experience, especially a board certified plastic surgeon since they spend years studying aesthetic medicine and have been reviewed by a panel of their peers (the board) as far as their ethics, artistry and skills.
Some patients are really cost-concious, but a difference of $100-200 is really worth it to get it done right. If you compare the results from a pysician who is really skilled and experienced specifically in Juvederm (and injects it daily) vs. a newly-trained nurse or a doctor who practices other types of medicine and recently started injecting, or does occassional injections "on the side," you can almost always tell the difference in my opinion.