That's a loaded question.....no pun intended! I think every woman is different, and you'll find many different answers from many different women. Variety is the spice of life!
However, I do agree....a large penis is not going to necessarily guarantee me good sexual intercourse.....that depends on the guy. So, I must agree with the saying, "It's not what you've got, it's how you use it."
However, I have to admit that I personally prefer a longer penis, and not a wide one. I don't know why, I sometimes wonder if it has to do with the fact that I'm tall. Perhaps my vagina is longer than other women? Is that why I prefer a longer penis???
From my experience (which is a lot), I would say an average erect penis is 6 inches.
PS - I've found that Canadians tend to have long penises, like I prefer.
