[ReptileHouse]

These situations are pretty close against against someone with out a more detailed read than "loose donk with post-flop aggro tendencies." For example,

Board: Jc 9h 4s
Dead:

equity win tie pots won pots tied
Hand 0: 47.515% 46.45% 01.06% 129681 2970.00 { KK }
Hand 1: 52.485% 51.42% 01.06% 143559 2970.00 { JJ+, 99, 44, AJs, QTs, J9s, AJo, J9o }

We're getting slightly better than that price to call. It's very, very close though. Tweak the range a bit and it can be pretty clear one way or the other. E.g., if he does this as a pure bluff very often at all, it becomes a clear call. OTOH, if he rarely does it with a one pair hand that's not an overpair, it becomes a clear fold.

When I see a bet like this from a donk, I tend to think, "strong, but vulnerable, hand." Two pair, especially bottom two, overpairs, etc.. On this board, the only reasonable two pair is J9. I would strongly weight villain's range towards J9 and QQ. Even overagrro donks don't often play sets like this on dry boards.

This villain seems aggro enough postflop that I can't see a call being horribly wrong. If it's incorrect, it's not by much.

That said, my tendency is to fold. I probably rival A5 in being a station (and not in a good way, he's a better handreader than I am by far), but when I have a very, very close decision like this, I tend to err on the side of folding. I'll admit my reason isn't the best one. It's mostly psychological. If I stack off here by getting the money in bad, it's going to tilt me and I'm likely to play badly for the next 30 minutes or so. I suppose you could say that I'm quantifying my tilt as additional -EV as part of deciding whether to call.