Both tales are strongly moralistic in tone, albeit with different messages to convey. This is perhaps related to the differences in character between the two narrators. The Wife of Bath is a bubbly, vivacious woman, someone with a vaguely alluring whiff of scandal about her; the Pardoner is a greedy, dishonest hypocrite who knowingly cons people into parting with their money for useless relics. Yet, both pilgrims narrate a tale that is at least semiautobiographical and in which they reveal something about themselves and all their sins. Perhaps this explains why the Wife of Bath and the Pardoner are two of the most recognizably human of Chaucer's characters.
The Pardoner, in his tale, is making a serious point: love of money is the root of all evil. He would know. His story is about three greedy men who look for the figure of Death. When they cannot find him, they come across a sack of gold pieces. They agree to split the loot between them, but each man gets greedy. They end up killing each other. Their discovery of riches leads them to Death after all.
"The Pardoner's Tale" is essentially self-serving; this is a similarity it shares with the "Wife of Bath's Tale." In telling his tale, he is trying to convince the other pilgrims that they are very lucky to have him on the journey and that they need to buy his relics to help cleanse themselves of the taint of sin.
The Wife of Bath, like the Pardoner, has a very high opinion of herself. She has led a very full life, to put it mildly, having gone through five husbands and travelled the world to go on pilgrimages. (A much more impressive feat than would be the case today.) Like the Pardoner, she is very wise in the ways of the world, and she loves the good things in life.
Her tale, like the Pardoner's, has a very important moral to it. A knight at the court of King Arthur has raped a comely young maiden. As a punishment, he is ordered by the queen to find out, in the space of a year, what it is that women really want. If he cannot find the answer or the answer is wrong, he will lose his head. Finally, after a long search, he comes across an ugly old hag who tells him that what women want most of all is to be in charge of their husbands and lovers. When he takes her back to the court, this indeed turns out to be the right answer. She bounces him into a marriage, and on their wedding night, she makes him choose between a life with her (faithful and good but ugly) or a young coquette (beautiful but capricious and unfaithful). He chooses her and voila! The old hag turns into a good and beautiful lady. They live happily ever after.
The knight has finally recognized that being truly rich means having and wanting nothing. The kind of covetousness he displayed in desiring the young maiden is no different from that shown by the three greedy louts in "The Pardoner's Tale." The main difference between the two tales lies in the fact that the Pardoner is trying to scare people into not loving money for its own sake. (That is his job, after all.) It is the method he normally uses in his sermons when he is looking to sell some of his worthless relics.
The Wife of Bath, however, is offering us a more positive moral, one that shows us what we must do to lead a virtuous life, rather than what we must refrain from doing. The Pardoner is a man whose prosperity relies on people being scared out of their wits and then parting with their money. The Wife of Bath, however, is independently wealthy and can dispense her homely wisdom without thought for material gain.