Bit of both. I have a regular I go an see, who is older, and been doing it for ages.However, she's not jaded, and we always have (dare I say it, "genuine") fun. Very relaxed, and easy sessions.
But then on the other hand, I also like the younger girls - early 20's - who of course, won't have been doing it as long, but are much hotter.
Of course, you can get the jaded old WG that's bitter and disinterested, but you can also get the same with a younger girl even if she hasn't been doing it long. The younger girls can also be a bit more "vanilla" as they are inexperienced too, so just go through the "BJ > miss > doggy > cum" sequence. Difference is, you can take charge a bit more with them, than an older one set in her ways.
But really, it just boils down to which are good. Get a good older one, and you're laughing. Get a good younger one, and you're still laughing (although probably cum quicker cos they're hotter
I'm generally a half hour punter, but with the older regular, I'm there most times for an hour/hour and a bit, and get more bang for my buck - pun intended! So I look at the little extra the younger ones cost as "hotness tax"