So not unlike your situation then?
The OP already has a degree, and has completed one year of both RN and paramedic degrees. She could probably get APL'd / credited for many of the duplicate requirements that she either has, or will gain if she continues with both paramedic and RN classes. It should also be noted that some bachelors degrees are only 3 years long in NZ
As for which one to choose...
Nursing is nursing - a job which will always be in demand regardless of where you do it. A job where if you get tired of one speciality, you can post to something completely different without changing your profession, title, or even your seniority in some facilities. It is also one of the few civilian jobs which can still facilitate certain visas for world travel assignments, unlike the paramedic (degree or not).
It's no secret that NZ Paramedics are moving away from the BLS SJA volly days of old (they do still have them) and into the Australian, British, and Canadian model of degree-based entry for practice. It sounds like it will be a good system to be part of in the years ahead.
On the down side - both jobs can be equally tiring, thankless, messy, smelly (not just RNs that deal with number 2s), often underpaid, and always have the potential to be on the receiving end of physical abuse.
For the OP, I can't advise you to chose one from the other. As I said, if you could do both I would certainly advise it. You don't need to do them at the same time, leave it a couple of years between courses. If you can't - it's your call.
Good luck anyway.
PS, Say "hi" to my Mother if you see her...she lands in Auckland at 1:40pm today as she is spending christmas with my Sis in Whangarei.