Are tire pressure monitoring systems accurate?

2 psi isn't going to make much difference. Set the tire so it's 1 psi lower than one gauge and 1 psi higher than the other. That's basically how silly it is to worry about 1-2 psi. Pick one reading and go with it.

You're actually interested in overall change, and rate of change. If you're losing 5 psi every day, it doesn't really matter that you started at 82 psi, or 80 psi. The level of change and speed at which it happens is what you should be interested in.