Just recently, in real life, in a month or so, I've seen two young girls who will probably remain in my brain forever or at least for a long time. One of them was a petite redhead, and I didn't really look at her body. She was maybe twenty or something, and just her being young, and redheaded, with strands of loose hair on her forehead and pale lightly freckled face was enough to make me stop and admire her. She was in a hurry to get somewhere, and she looked timid and energetic at the same time, and I doubt you could really see a lot of mature women like that, in that combination: fiery red hear (even red hair, though it does not go grey, loses its intensity), fresh face without a single wrinkle, shining blue eyes — and the demeanor that fit that, just as you would expect from a young girl... And another one, maybe also twenty or twenty-five, I saw only from the back, and she was wearing a very shirt skirt, and she had thin but very feminine legs in almost transparent or body-color stockings. It instantly made me think (a possibly strange though, but that's how I am): even if a guy had such thin legs, they would not look like that at all. I mean, all the protagonists of those "gender-bender" manga and anime are skinny dudes, and that's the only way you would assume they get away with dressing as a girl. But there is more to that (obviously). And later that day I searched for it, and yes, there are many ways in which male and female anatomy differs if we talk about legs specifically: bone structure and curvature (and even the angles between the bones and joints), muscle and fat ratios etc. And again, this was the whole combination: a mature lady would not be wearing such a short skirt (and even if she would, it would not fit most mature women), and the legs of that young girl were just that — young, and fit, and thin, and sexy in their own unique way
And again (one more time), if you asked me about more mature women I have stored in my brain, there would be just as many. One of the most vivid memories like that is from an age when I was probably 20 myself and had a university teacher who was 25—30, maybe even older. She had another perfect combination: she was smart, and energetic but already seemed burdened with her role as a teacher a bit, or at least she had a lot of things to do and was in a rush as well, but it seemed like a different kind of rush. She had quite a big bottom (I don't feel like using "ass" here since I knew her well) and she wore a business suit (she was an economics teacher) that only accentuated that. So, a classic OL but in real life. I still remember how I met her in the street near the campus one day, and we talked a bit, and said goodbye, and was mesmerized watching her leave... just watching that big bottom of hers in these trousers... Yeah, if that was a young girl, even with an ass equally big, it would not be the same. It would not feel the same...
And finally, there are some cases when the contrast between what you expect and what you get also works great: imagine a young girl who is also very smart and has travelled the world, or an older woman who still has just as much energy about life as she did in her teens... I'm talking more about non-sexual things again, but hey, I think the older you get, the more you see this spectrum: there is something sexy about "dumb bimbos", and "life-hardened gyaru", and, say, an older woman who will fuck you herself without you doing much just because she needs it: she'll just get that thing of hers onto your thing, as hard as she needs, and you just pray to God Almighty that you're hard enough throughout...