One argument I've seen deployed in defense of annihilationism is that annihilation is an objectively worse punishment than everlasting misery. I believe Chris Date uses this argument. I think the argument goes something like this: according to annihilationism, the damned have more to lose since the damned lose their very existence. They have everything to lose, in contrast to everlasting misery. And that's an objective difference. Assuming that's the gist of the argument, it suffers from several problems:
i) The general principle seems to be a quantitative difference: more of something or less of something. In particular, something bad. Quantitatively worse.
But by that same metric, everlasting punishment is objectively more of something (bad) than temporary punishment (annihilationism). In that respect, the damned have more to lose if they face everlasting punishment rather than temporary punishment. Everlasting punishment is longer, indeed, infinitely longer, than temporary punishment. So the quantitative comparison cuts both ways.
ii) In addition, it's nonsensical to act as though the subjective effect of punishment is secondary to the nature of punishment. Take Islam. On the one hand it has a fiery hell. On the other hand, a suicide bomber is instantly transported to the heavenly whorehouse. But if subjective experience is inessential to what makes an experience punitive, then what makes hell hellish and paradise paradisiacal? Why couldn't you trade places?
Suppose you say what's pleasant or unpleasant is subjective. But if you decouple punishment from pain (whether physical or psychological), then what makes punishment punitive? What makes suffering qualitatively worse than pleasure? If pain and punishment are separable, then punishment could be pleasant. Sensual enjoyment could be punitive. But isn't that absurd?