I would (and did haha) pick SLP all the way. I am currently an RT (respiratory therapist) and while I love my work I am pursuing speech for several reasons. The market (where I am) is over-saturated w/ RTs and it seems to be headed that way with nursing as well, according to my co-workers. So stability is lacking in my field, to say the least. I also feel as though nurses are incredibly under-appreciated, and tend to bear the brunt of criticism and blame from all sides. This includes the patients, the patients' families, and the doctors. To choose nursing, and to be happy and fulfilled in this career, I think you really need to have a VERY strong calling for it.
I'm picking SLP in part because I am drawn to having a schedule (working for a school district) that mirrors my children's school schedule. That being said I will likely want to work per diem in the hospital setting as well, as that is where my roots are. I also like the idea of being able to take on private clients on my "own time" so to speak. My mother in law is a retired speech pathologist, and was able to take on private cases during school breaks, and also after she retired from the school district for extra income. In addition, even if you don't think this will be an issue for you, there is a greater degree of respect for SLPs vs RTs or RNs, in my experience. This is I am sure in part due to the higher level of education required for the position. If you want to eventually pursue an even higher degree of education, I believe you have more opportunities in SLP as there seems to be a shortage of applicants. (Meaning doctorates and PhDs etc) So if you want to pursue teaching and/or research, you may have a better chance at finding a program and funding than in other fields of study.
A professor of mine recently gave us a talk that I found very inspirational. He said that because SLP is still a relatively "unknown" profession, you have the ability to carve out your own niche in the field. You can become "an expert" in whatever area you are drawn to where not much is known. He said that it was important to always have something going "on the side" - take on extra projects, become involved, and guess what? You will get noticed. You will be considered for more opportunities. You will gain even more respect. I find this all very exciting.