It's not a matter of him 'doing better'; Dan likely prefers the younger women because they're less likely to call him out on his nonsense (while women his own age are more likely to not put up with any of it).
Why hook up with a mature woman who expects more out of you when you can have a gullible, starstruck groupie who'll worship the very ground you walk on/do anything to please you?
I suppose I should have clarified by "better" I meant someone young who won't demand too much out of him so long as he's got some level of fame and a decent amount of cash to throw her way.
Of course, as others have pointed out, most people in their late teens/ early twenties don't really think about debt and savings too hard at that age (colleges get away with charging out the ass for a reason, am I right?) and also tend to hold people who have even the smallest amount of fame on a pedestal. But once they hit their mid-late twenties/ early thirties they tend to think about their future a bit more and also have learned that most celebrities are about as intelligent as the average person, sometimes even less so.
So, that's about a five or so year age jump, right? If what @MahFibro! said is true and Dan does normally shoot to date women around their late teens/ early twenties, then I guess the math adds up.