I have worked in a clinic staffed primarily by NP's for the past 5 years, so I think I have some perspective on this issue. Here in OR, NP's can practice w/out a doctor present, which gives them a lot more independence than in some states; also, they certainly have a lifestyle advantage in some ways, as their postgraduate education is only 2-3 years (master's level), with no residency, and most NP jobs require little or no on call. At my clinic, the NP's basically function as doctors: they perform exams, make diagnoses, prescribe medication, etc. The pay range certainly isn't bad--$50,000-70,000+--especially considering that most don't graduate with the mountains of debt MD's generally face. Also, the demand for NP's is rising, as HMO's and hospitals are using them more and more in place of doctors for routine care as a cost-cutting measure.
So that's the good stuff; but there is obviously a downside as well, depending on what you're looking for. I have certainly considered both degrees as options, but came to the conclusion that NP is not for me. Even in OR, which is a fairly liberal state as far as who it allows to practice medicine and the restrictions it places on them, NP's have to operate under strict guidelines if a physician is not present when they see patients. At the clinic where I work, there is a set of protocols they have to follow that states what they can and can't treat, and most non-routine care has to be referred to an MD. So, autonomy and freedom to see and treat patients is restricted; and in many states, NP's can't even practice unless a doctor is there at all times looking over their shoulder and approving their decisions, and they can only write Rx's in some states as well (geographically limiting, if you want more freedom to practice). Of course, there is less responsibility and liability directly on you, but you trade that for the ability to have an unrestricted practice. It seems that the trend is towards giving more of these freedoms to NP's and PA's, but it will probably be a long time before NP's nationwide have even the practicing rights given in OR.
You are also restricted in the types of medicine you can practice: NP's can focus their education in areas like pediatrics, family medicine, women's health, and psychiatry, but not specialized areas like surgery (although I have heard there are surgical PA programs) or dermatology. This is fine if you know you want to be a general practitioner, but if you are considering a more specialized branch of medicine this could be frustrating. I don't know what area of medicine I want to practice in yet, so I want to keep my options open. Finally, the education you receive as an NP differs substantially from that of an MD. While I have been consistently impressed with the skill and knowledge of the NP's I work with, their education is neither as broad or deep an exploration into the functioning of the human body as the one you receive in medical school. To some people this matters more or less, but part of my motivation to enter medical school is a fascination with the human body, which I woud like to understand as deeply as I can. NP's receive a more than adequate education in this area, but if you desire a more complete understanding of the human body, medical school is obviously the best place to receive this.
So, being an NP can be a great way to have a satisfying career in medicine in which you can practice a wide range of general medical care, without the cost and time of going to med school, as long as you are willing to accept the restrictions of the profession in terms of autonomy, areas of practice (both specialization and geographical), and education.
