Women's MMA is definitely younger than men's, but at the same time, the women have the luxury of not having to reinvent the wheel, as (to my knowledge) there are either none or very few female MMA gyms, so they're training with the guys, and have the same ~20 years of MMA history to draw from in what works and what doesn't.

The interesting thing about the Rousey's armbar is that everyone knows it's coming, and presumably, would look to defend against it above all else, and yet she still has an astonishing number of wins with it. A lot of that has to do with her being well-rounded elsewhere, and a lot of is has to do with the fact that she's really, really good at armbars.

Women's MMA is primarily disadvantaged by the dearth of women in college / high school wrestling, which means that most of them are starting later than the guys who graduated from greco roman wrestling and parlayed that into MMA. It's a big advantage, due almost entirely to discrimination, but one that will likely be obviated over time.

Ronda, on the other hand, grew up in an athletic household as the daughter of the first women's judo champion, and that mother routinely pushed her towards a similar path. She maybe didn't get a chance at college wrestling (or maybe she did, hell if I know), but she got the relevant training regardless, which puts her ahead of the rest of the pack.

Ronda's got a leg up, and it probably won't persist ad eterneum, but for now, and probably the immediate future, she's the best, and she's earned it. If she stops being the best, the question really is whether the talent vacuum rushes in around her, or gets occupied by the single person that beat her, and all that.