While Lady Catherine and Mrs. Bennet come from two very different social classes, they have more in common than they may think. Here are a few things to think about:
1. Both women are mothers to daughters. This causes both of the them great concern over the future of their children. Mrs. Bennet obviously has more to worry about in terms of the sheet number of daughters she has to try to get married, Lady Catherine needs to worry about the social implications of a marriage for her daughter. The pool of appropriate and eligible men for Anne is significantly less than for the Bennet girls. It would be inappropriate for Anne to marry anyone of a lower social class than her, especially if there were no money or land to come into the marriage. Nobles married with the thought of maintaining wealth and status. The Bennets are concerned by economics, but Elizabeth declares early on that she will marry first for love -- and she is in more of a social position to do that. This whole situation is why Lady Catherine is upset that Elizabeth could marry Darcy. Darcy is of the appropriate class to marry her daughter and is one of a only few who would be acceptable. Elizabeth could marry any number of eligible young men and be perfectly suited and happy. All that said, BOTH mothers want what is best for their daughters, especially in regards to financial security.
2. Both women are a bit "know-it-alls." They both, in their own way, think they know what is best for everyone around them and are not afraid to express those ideas.
3. They are both rather rude. Mrs. Bennet speaks inappropriately out of place at the Netherfield Ball when she loudly proclaims that Jane and Bingley will be married. Lady Catherine is judgemental in her "interview"/conversation with Elizabeth when the Elizabeth visit Rosings.
4. They are both strong women who are not easy to stop or dissuade from their opinions.
5. They are both concerned with family reputation (though Bennet less so).
One of the most significant differences is each of the distinct social classes and how that influences other aspects of their characterizations. Mrs. Bennet and Lady Catherine live in different spheres. Lady Catherine presumes to be the master of all around her. Mrs. Bennet only barely presumes to the master of her household.
Lady Catherine de Bourgh shares a few similarities with Mrs. Bennet in that both women want to marry off their daughters, they want to marry them well, and they do share the same preoccupation that, being mothers of females, their daughters will never attain social equality nor any form of advancement unless they are married to someone who can make them come to some property, and status.
However, they are not as similar in that Lady Catherine seems vindictive just for the sake of class, while Mrs. Bennet's main source of concern or detestation for the aristocracy comes only through her personal dislike towards Darcy. Darcy, however, earned this specific dislike from Mrs. Bennet because he was doing everything in his power to become disliked.
Hence, both women have same social preoccupations but Lady Catherine is by far less like-able than Mrs. Bennet-although Mrs. Bennet is not exactly a character that we could tolerate reading about as a main character in any story for her tendency to talk too much, too loud, and for being so obnoxious.