Hi,
It's better to do it than not to do it. In other words, it certainly won't hurt you to list professors you'd like to work with, so long as you seem genuine about your interest in those scholars, but it can hurt you to not list them. Some schools don't mind one way or the other. Other schools will evaluate your application lower because of it. A DGS from a top 20 school, a school I was in the final pool for admittance (but ultimately didn't get into), called me personally to talk about my application. The ONLY reason he said I did not get in was because I was missing a paragraph from my personal statement about which professors I would want to work with there. Ultimately, when it comes down to those last 30 people and the school can only fund 12, every last detail about your application WILL matter. The rest of the personal statement, my writing sample, GREs, CV, undergrad record, etc... were all considered excellent. For what it's worth, when I explained to the DGS that I was actually TOLD by a professor of mind from undergrad that including that list didn't matter at all, that DGS said I should have called to ask if his school preferred the list of professors. Go with the list, but don't make it overwhelm your personal statement.
