Interesting question. I tried to start a thread similar to this several months ago. Deleted. Nonetheless, I will venture an answer to your query.
As far as physical attractiveness is concerned, I believe the breasts are the lynch pin of sexiness. They serve as hostesses, if you will, to what could be a bountiful serving of femininity. I'm a big fan.
With that said, don't dismiss the behind. It serves a very important purpose in the courting of potential mates. Too small lends one to believe that the woman couldn't withstand the rigors of childbirth more than 7-8 times. Also, she may be too fragile to wrestle for entertainment. Too large of a behind shows an undisciplined lifestyle and potential health problems. However, never discount the old wise saying "more cushion for the pushin'". It's a delicate walk that many men have tried to master for centuries.
And finally, the vagina. An odd looking creature that has caused divorces, crime,
war and years of punishment because of bad decision making. People have committed murder over access to vagina. Men will do almost anything to access the vagina. And if/when a man is fortunate enough to find a willing woman, often times there is a price to pay. Literally and figuratively. Free vagina does not exist. It's like the fountain of youth or Atlantis. In fact, it is my belief that DeSoto and Magellan were both looking for nothing more than the proverbial "strange". If you are lucky enough to actually have sex what follows isn't pleasant. Talking, snuggling (whatever that is), kids crying behind the locked bedroom door, and in some cases, payment for services rendered. But we still do it. Why? Procreation is messy, often frustrating and filled with potential dangers. The answer is much more simple than this diatribe I have authored, it feels fabulous. The best thing ever.
Vagina wins. Breasts and the female posterior play important roles in the courtship. But ultimately, it is just to get some *****.
Thank you and good luck in lifes' journey.