I guess I'm in the minority on this one.. Mr Bennett is one of my favorite characters in the book, and this speech is one of my favorites of his!

There have been other comments about Austen's novels being "on the cusp" between 18th- and 19th-c styles -- Mr Bennett is a very 18th-century type of character, the stock figure of the "old philosopher." This type of character is comic because he processes everything through logic, and uses reason as a guard against feelings of disappointment, sadness, passion, etc. He may reason his way out of positive or negative feelings, distrusting all emotion as deceptive and short-sighted.

So here Mr. B is playing the "philosophical" game/joke of turning bad feelings (disappointment in love) into a reason for being happy, and pointing out the similarities between the HAPPY experience of getting engaged and the UNHAPPY experience of getting jilted -- both experiences involve a young man, draw attention from other girls, and provide a break from routine. Through logic, the philosopher can regard the emotional extremes of satisfaction and disappointment as equally stimulating and valuable.