Depends on what you want...a fling or a relationship.
To be honest, if you're looking for something long-term it's better to have the personality be there with good looks. I was married for several years and while she was very cute (7.5) she was NOT the most attractive woman I ever slept with. But too much of ANY woman and they will begin to look the same. But if it's someone you have a genuine connection with and enjoy to be around them then they are LTR material.
If you're just looking for a good time then obviously the 10 is the way to go. Thrill of the hunt and to the victor go the spoils.