If I were in a "you can only have one" situation, it would be NV, absolutely no questions asked.
Thermal is an absolutely awesome tool... for detection and engagement. If that's all you're worried about, then perhaps thermal is all you need.
NV allows for movement, stealth, positive ID, navigation, etc.
As I've said before, if all you're concerned about is hunting hogs and 'yotes from a fixed/semi-fixed position on your own property and/or terrain that you know well, thermal alone may be enough for you.
But if you're trying to be prepared for anything beyond that, whether it's a natural disaster that knocks out the power, or full-on Red Dawn scenarios, then NV will be infinitely more useful--because ultimately, detecting and engaging is only a small part of what you need to be able to do in the dark.
~Augee