In my experience...
I have been with girls younger and older than me. I am 32 and I dated a 35 yo, I have dated mostly 25 and 26 yo. I dated one one year younger only and one 9 years younger but she was 19.
Now...
Men are atrracted phisically the most, they like good bodys and specially, they liek to be the head in the relationship, to have the control.
On teh other hand girls like to feel protected, just a male with experience can give them the sensation.
So, everything starts from those stereotypes.
If the girl is too young she is just... too young! and when she is very close to your age there would be a situation on "who is the boss". When she is older is easyer to organize the papers.
Now I am 32 and my GF is 26, the age difference is perfect. I could handle some one up to 29 average or 21 the most.
The problem is: where are we in out time line?
I still creating my business and I am not ready for marriage. My GF is graduating and she is not prepared either.
If the girl is your age and you are aroudn 24 probably she wants children, it is an impulse and probably she will look for some one older who can provide her the "security".
My GF is not into kids now, she is into traveling and I am ok with that even I do not have the resources yet because I still growing in my business, but that si the regular situation.