I used to think of a list of reasons why it's "good" to be with someone younger, and some of that may be true early in the relationship. But when you've been with a partner for as long as I have (22 years), age related things go away and it's just like being with any other person. In the long run it's personality compatibility, shared values, common interests and acceptance of each other as people that far outweigh any benefits or drawbacks of your partner's age. Just like it is with same-age relationships.
Like Abraham Lincoln once said, "You can't believe everything you read on the Internet."