Upon further reflection, I think the question of "how much of the pain/suffering/unpleasantness/etc. from a given even happens on the spot, and how much lingers on in the memory?" has an answer that wildly varies, even for the same individual.

The worst physical pain I ever felt involved a certain surgical operation, but it causes me no discomfort whatsoever to remember it; conversely, I once got stung by an unknown insect while still half-asleep, and the thought still makes me twitch and clutch at my neck. On a more mental level, there are a few seemingly random subjects that make me flinch and feel burning shame whenever brought up, because almost a decade ago I happened to make a fool of myself in conversations that involved them; yet those were by no means the most sorrowful moments of my life, or even the most embarrassing.

So I would consider the question "would you take X pre-memory wipe, or Y post-wipe?" highly dependant on X and Y. And yes, I find myself agreeing that X='condemn a stranger to torture' would be exactly the kind of event that inflicts the majority of its suffering through memory and regret.