First, don't go into any profession with money being your deciding factor. Nursing and OT are both professions you will burn out of fast and regret if you don't truly want to help people and have the patience to work with people going through the most difficult times of their lives. Also, nursing and OT are very different professions. Nurses generally work 3 12 hour shifts in hospitals including required weekend days. OTs in many clinical setting work M-F 9-5 kind of schedules. In nursing you care for patients and go by the medical model, you work directly under doctors orders and give medications and follow very specific protocols and treatments based on a patient's diagnosis and illness. You need to be able to deal with all bodily fluids, death, emergency situations, and the responsibility of someone's life under your care.
In OT everything is trial and error as far as treatments you choose with your patient- it is based on the inidivual's deficits and needs of your patient. You teach patients how to take care of themselves and function at their best mentally, physically, emotionally, you do not take care of them. You need problem solving skills to figure out their deficits and why they have them.. and you need the ability to think outside the box in OT because you have to create treatment plans clients will find meaninful and engage in. You need to have empathy for people with all kinds of deficits and disabilities. I strongly recommend observing OT in the hospital,and other settings. It is very different in each kind of setting and what populations you work with. In a hospital and skilled nursing facility you will also get to see nurses work.
With health care professions it all depends on what area you live in, years of experience, how much you work, and what setting. All these variables need to be considered. Ex. in acute care in my area new nursing grads make ~ $67,000 out of school MOTs ~$73,000. However, OTs have a salary in many settings such as a hospital, where RNs do not. RNs can work overtime and get time and 1/2 and make $100,000 if they work overtime a lot. OTs can also make more by working in contract positions on top of their regular job, or in private practice. It all depends. RNs have more upward mobility in the longrun as far as management positions. From what I've seen, most rehabs have physical therapists as management over their rehab staff.