I have always thought that the relationship here is about the same as in the male. If a man's size is related to penis size, then the vagina is related to a woman's size. I've been able to test this theory over the years, and can tell you it isn't related to the height of the woman or the width of her butt. However, black women versus white woman-- now, that's a different subject. As with men, women vary quite a bit. I'm thinking that the depth of their vagina can vary perhaps 3 inches, but what's difficult to measure is the angle and curve. That makes for a little different feel.
I think the most notable difference isn't the depth but the width. Some girls are pretty tight, but the more narrow ones might also be deeper. It depends, but less on how large a person they are.
All women like a hard-on that's long enough to hit their cervix on occassion, even though some of them claim it isn't necessary, they are just being generous. They will mostly settle for anything the guy has if they like him, but I've found they really love it when you get the thrust just right and are lightly bumping it, either each time, or every 3rd or 4th time.