If you have a rainy-day fund and then enough money that there's absolutely nothing useful to spend it on... and if you feel it's gonna make you happier... get both, no need to prioritize.

If you are not in that situation and have to prioritize, then don't get either, and do just about anything else with the money. Spend it on home improvement or crack cocaine, either way, you get more in return.

Plates are this cool thing that every other prepper thinks they need, until you realize that they are really heavy and hot and bulky and just uncomfortable and impractical to wear. Then they end up in the closet. I can't talk you out of buying them, but mark my words.

Night vision... at least you get a bit more use out of it, especially thermal, because you can film your dog or squirrels in the backyard and it looks cool. You can also sometimes use it around the house... it can show you studs, ductwork, piping, etc, through the walls. So still not a useful prepper tool, but you can do some other things with it. Far more expensive than plates, though.