This question is too big to be addresses completely on YA--you will need to do some research. (PS it's Physician Assistant)
Neither of these are "best" they are just different.
All take about the same amount of time once you get in the program (as they are all masters) but have different requirements to get in the door, so to speak.
A masters RN (are you thinking a clinical nurse specialist?) and a NP (also a masters) require a BSRN and some experience as a RN. A masters PA requires a pre-med type bachelors and some type of experience in the medical field (EMT, paramedic, RN, med tech, Xray etc) and each school has the required # of hours you would need. There are a very few bachelors PA school but would highly advise the masters--as that's they future of the profession.
Salary for the NP & the PA are very comparable (depends on where you practice (state, clinic, hospital etc) and which specialty. The average PA salary is about $75,000 and up currently; or about $50/hr. The plain nursing master may be a bit less-- but as you did not state what that master is for--so difficult to answer for that.
There are school all over--for PA check the aapa.org. They are pretty competitive however (think med school).
"Rank" is really not an issue here. You are a midlevel practitioner; everyone else but the doctor is under you so to speak, and the MD is always on top.
Type of work--again an enormous question--depends on you location, your specialty, your training. All PAs are family practice (except surgical PA schools) and then specialize either on the job or in residencies. NPs can be family practice (more general) or go to a specialty program (ie GYN NP, peds NP & can then only work in that specialty).
In general, you do what a doc does up to a point: see patients, examine them, diagnose, treat, write prescriptions, order & interpret tests, do procedures--depending on your training.
It just depends if you want more of a medical focus (PA) or a nursing basis focus (NP). Look a t both their national web sites & shadow/talk to both.