I really honestly believe that the vast majority of LORs and PS's (probably over 50%) end up neither hurting nor helping an applicant
Amen to that. Basically, if you know what you are doing (and if you are posting here, you're 90% of the way there), then it's practically a given that you're going to have good-to-great LORs and a good-to-great PS - just like everybody else who's done the research to figure out how the admissions game is played.
Where it will help is when you get compared against the applicants who just go through the motions - with LORs like "Joe Schmoe was a good student in my class, I gave him a B+. Other than that, I don't really know him that well..." and a PS that explains they really have wanted to be a lawyer since they were 5 years old because their dad was one and they want to correct all the injustice in the world.
So, your LORs and PS won't really give you an edge against me (your GPA and LSAT have already done that!
, but both of us should get the edge on poor old Joe.