I think it matters how many partners a woman has had if you are in a relationship with them only because high partner counts are indicative of a woman that doesn't '"invest" much of herself into a relationship. If you are looking to just get laid, by all means find the biggest slut you can. But if you want something more serious, a woman who has gone around the block scores of times will love you and leave you much quicker than a woman that has only been with say 5-10.
As far a vaginas go, they come in all shapes and sizes. Some women are wrecked after a giving birth, but some bounce back. I dated a gal with one child, she had been with 4 men before me, was very slim and fit( I could almost wrap my hands around her waist) and she had the loosest vagina I have ever come across. COmpare that to my 'Emergency Backup Chick', she'll fuck anything with a penis and is a bigger gal, (black guys would call her thick, I would only call her at 3 am) and she is packing a greased fist between her legs.