This is largely a matter of opinion, but I would argue that the Wife of Bath's Tale is more deserving of Harry Bailey's prize than the Pardoner's. Generally speaking, the Wife's tale is more engaging and more original.
Furthermore, there's nothing remotely predictable about the way the story develops. Although we might suspect that it has a happy ending for the errant knight forced to find an answer to the queen's question on pain of death, how he achieves such happiness is by no means certain until right near the end of the tale. When the hideous old crone that he's married turns into a beautiful woman, it's a fair assumption that not many of us will have seen it coming. It's this twist in the tale, more than anything, that makes the Wife of Bath a deserving recipient of Harry Bailey's prize.
As for the Pardoner's Tale, it's perfectly workmanlike, but it's not much more than that. It's a boilerplate moral parable on the dangers of greed whose ending can be seen a mile away. Some...
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