Hi fantasyfan, I agree with you that Persuasion is a morally complicated world, while P&P is playful.
Elizabeth Bennet sees Wickham's victims as deserving of what they get (like Mary King), an attitude she later decides is owing to her undue preference for him. It is a comedy because unlike Mrs Smith she can reflect from the comfort of her parental home, rather than face the rigours of married life to an unreliable man.
Legally, marriage meant subordination for women. Sir William Blackstone (Blackstone Law Reports) summarized in 1753 that: "By marriage, the husband and wife are one person in law: that is, the very being, or legal existence of the woman is suspended during the marriage, or at least is incorporated and consolidated into that of the husband: under whose wing, protection and cover, she performs every thing".
I found an interesting website which discusses a few different options an Eighteenth Century woman could take. http://www.umich.edu/~ece/student_pr...way/index.html
Despite this loss of an independent legal identity marriage was more often chosen over the alternatives. But as the Austen sisters can attest it was possible to earn your living if you pooled your resources. But without independent financial means, women trod a tightrope of deference and defiance to maintain the household.
The alternatives to marriage were occupations in household service and prostitution. Sharpe, Pamela. Adapting To Capitalism: Working Women in the English Economy, 1700-1850. New York: St. Martin's Press, 1996.
What makes Persuasion so compelling is that Austen is able to put social expectations and hypocrisies to the test. The plotting and characterisation is all the better for it, because of her wit and perceptiveness.