I cannot think of a single positive to dating older women. Let me break everything down here...
Age 18-23: If you're looking for a life-long companion, this is the age zone to focus on. Lots of women in this age range are still in their early years of dating. They aren't alpha widows. They are still prime picking for to you easily make your way up to the top of their high score list. Their minds are like fresh, soft dough. You can easily make an imprint on their emotions. The deeper the imprint, the more dedicated they will be to you.
Women in this age range are less likely to be littered with children, orbiters, and ex-BFs that they keep returning to. Having children isn't high on their priority list at this time. They may be a bit high energy and a bit immature, but this is only temporary. Women are generally done maturing by age 23.
Age 23-27: Women in this age range are the most enjoyable. The decent ones have their 5hit somewhat together. They have a job, perhaps their own place, they're not as high energy and stupid as they were in the previous range. Having children has entered their mind, but it isn't a desperate need yet. Some of them already have children, some are married. Most of them have the top spots of their high score list filled with some a55hole ex-BF which makes them more difficult to lock down as a life-long partner since you're competing with some guy who's already made his emotional imprint on her, and the dough has started to dry out, making it more permanent.
Age 27-29: Age 30 is coming! Age 30 is coming! The sky is falling! The sky is falling! The clock is ticking! Must have a baby before it's too late! These women are beginning a serious search for a sperm donor. Others already have children with some guy they kicked to the curb. The top position on her high score list is stories high, and the dough needs to be chiselled in order to make your emotional imprint on her. Her looks are starting to decay, and gravity is starting to pull body parts lower to the ground.
Age 30+: All of the above. If she's childless, her search has become even more desperate for a sperm donor. Watch out! She will poke holes in condoms, miss her birth control, fvck some other guy to get pregnant while she's with you, etc etc. These women are DANGEROUS to become involved with. The top of her high score list already has some other guy there. All you're doing is providing the sperm she didn't get from him. She will toss you away once she gets what she needs.
To summarize, age 23-27 is great if you like having sex with good looking women without having them try to lock you down for children. Age 18-23 is best for those who want a life-long companion, because you get the best of every stage. You get the top spot on the high score list, you get the attractive and stable phase, and you get the "I want kids" phase, but they're going to be YOUR children.