In Austen everyone suffers from the "everybody on the make" syndrome. Listening to Pride & Prejudice, I was struck, moreso than I have been in the past, by the hardheadedness underlying all that sensibility. Elizabeth gets angry over Darcy's interference with Bingley & Jane, but her anger is undercut by the fact that everybody is interfering with everybody all the time. Her aunt gives her advice. Elizabeth gives her sister and Charlotte advice. Charlotte gives Elizabeth advice. It's just an orgy of opinions. What is comes down to is: everybody wants love but nobody wants to be poor.
Now, the most respectable of romance novels, such as Georgette Heyer's, try to capture this on-the-make quality of Regency life. Georgette Heyer, who did a large amount of research on the dress and setting of the period, never marries her lords to peasant girls. She's no more democratic than Austen, and there are some Austenish ziggers in her comedy, although in general her comedy is lighter, fluffier and less consequential. In truth, Heyer's writing can be very funny, but she was less concerned with underlying causes and more concerned with writing a sweet story. Everyone is on the make but somehow that fact never rises to the surface. Heyer keeps it carefully under control. Lovely young ladies turn out to be heiresses. Handsome young men turn out to her heirs. Supposed changelings turn out to have Viscounts for fathers. Don't worry. There's no angst here.
This brings us to the other difference between Austen and romances, and it is, I think, the major one. Austen is about story. Most romances are about plot. Plot is the line of story: this happens, then this, then this, now this. Story is best described using a Stephen King image. He describes the process of writing as uncovering a skelton. The story is already there, whole, intact. It just needs to be brought to the surface. With plot, the end is always a twist, a change of fortune, the turn of the wheel. In Heyer's These Old Shades, the non-changeling changeling gets captured by her despicable father, rescued by her saturnine lover, presented to all of Paris, confronted with the supposed fact of her illegitimacy at which she runs away to save her lover from her supposed bad reputation. She is finally recovered by her lover and restored to all her rights and privileges (I'm using lover in the old sense of the word; this is Georgette Heyer; nobody sleeps with anybody until they are married, although the dandies and members of the ton always have had mistresses that occurred offstage and long before the plot began).
Now, in all honesty, this is a whole bunch of fun. But it isn't the same as story. With story, the ending is incipient in the beginning. There's inevitability about it. No twist is necessary to bring about a particular ending. The ending already exists, inviolate, known (although not necessarily revealed yet to the reader). The parts of the story hold together like a statue, a shape. As one reads, one gets a sense of an emerging totality.
Take Elizabeth and Darcy. I wrote earlier about how Darcy & Elizabeth loved each other for who they were, rather than what feats of flirtation they performed (my sister Beth reminded me that Darcy was attracted by Elizabeth's "bright eyes" and Elizabeth was impressed by Darcy's management of his estate). On the other hand, both Elizabeth and Darcy undergo an enlightenment, a point when they reorganize their thoughts and feelings. Elizabeth is angered, then humiliated and aggrieved by Darcy's letter. Darcy is angered, then embarrassed by Elizabeth's accusations of "ungentlemanly" behavior. But the argument has been coming for a long-time. The mutual feelings of attraction (I side with those who think that Elizabeth was always attracted, or at least interested in Darcy) and irritation have been growing for awhile. Elizabeth's visit to Pemberley isn't contrived. Since, as Beth points out, Darcy's property is an extension of himself, Elizabeth's arrival there is, on a metaphorical level, simply one more piece of the relationship pie. Darcy's intercession with Wickham & Lydia isn't a lucky chance. It is forecast by Darcy's behavior at Netherfield Park where he purchases reputation at the expense of Lydia's future (who might not matter but Elizabeth and Jane certainly do), behavior he must rectify.
This quality of inevitability is true of all Austen's books, including, especially, Mansfield Park. Much praise has been heaped up concerning Mary Crawford's wit with the follow-up implication that Austen herself admire Mary Crawford and that Austen only removed Ms. Crawford from the book as a kind of plot contrivance. But Edmund's disillusionment is a long-time coming. The wit of Elizabeth is not, contrary to speculation, reworked in Mary Crawford or, if it is, Austen was older and wiser and knew that wit can be a mean-spirited tool when used by superficial and self-absorbed individuals. Edmund's disillusionment is there from the beginning and no twist needs to bring it about. Austen's interference is only to remove his blinders before he proposes. (And since the said removal comes through Henry Crawford's behavior, it too was foreseeable.)
I'll go so far as to say that all great works have story, rather than just plot. However, plot isn't a bad thing. My abilities as a writer, with a few lucky exceptions, extend about as far as plot. Better to have something happen, after all, than just profound navel-gazing. Still, in the end, story reigns supreme.