Hello folks,
If you really looking for safety in HEMS operation, all should have both of them. NVG without IFR knowledge and skills might cause problems also. Think, if you are in the middle of somewhere and you are loose your NVG expectedly. That's happen in real life occasionally. You might have inadvertment phenomenom and to fix this situation, you need to have some way out.
For my opinion; ME SP(or MP)IFR with NVG. No money, no funny.
Hostile