In general we should call small bets more often than big bets. This is simple game theory, and there is something called “Minimum Defense Frequenzy” or MDF, which we should at least understand if not always follow. MDF is basically the percentage of the time, we must call to make
bluffing neutral EV for our opponent. If he bet pot on the river, it needs to work 50% of the time, so MDF is 50%.
Our default should therefore be to call 50% of the time, and typically of course with our best
hands. Or sometimes with those hands, that have good removal. Like maybe there are 3 diamonds on the board, and we hold Ad making the nut flush impossible for him to have. This is the baseline, and then its all about reads and adjustments. Individual reads are, well, individual, and since you are the one playing this particular opponent, only you have them.
If I am to give, what I think is a bit of a population read in the micros, then I will say, that a pot sized bet on the river tend to be a nutted hand. Maybe the opponent was slowplaying something, but we failed to take the bait, and now he is trying to make up for lost value by betting full pot on the river. Unless I have a really good hand, I tend to just fold and let him win a small pot.
On the other hand a pot sized donk bet on the flop is often some kind of weak hand acting tough in the hope, that everyone will fold. Maybe a hand like A4 or K7 on 742 two tone board. If I have an overpair or a good draw here, I am certainly not going away, and I might even raise.