I've been in the dental field for several years and I would like to add that there are several
health benefits to having a great smile!
If teeth are in cross bite or misaligned, there is an increased chance of plaque buildup and food buildup in between your teeth, which is a trickle-down effect because the more food buildup, the more plaque; therefore, the more concern for periodontal disease and gum disease. Improper bite also means you can't chew food properly, which can lead to gastrointestinal problems.
Properly aligned teeth have been known to reduce headaches, pain in the face and neck, and stress on the teeth and gums.
Also straight teeth are a sign of affluence and wealth - just the way it is. A nice healthy looking smile makes you more attractive to others, and having straight teeth can improve your lifestyle greatly by boosting your self esteem and confidence. You might even get a better paying job in the future due to the fact that your teeth look great (not kidding - it's all about perception). It's just human nature to be attracted to things that are symmetrical, that's why in most cases crooked teeth are considered to be unattractive.
There is not alot of health benefits of having nice breast, except for the esteem issue. I say... teeth now, breast later!
But if I were a man and it was all about the lay... I'd definitely say breast. Just her around or tell her "here, bite on this" and use a pillow/blanket to cover that shit up!!