Do men value physical appearance more than women mainly because men are more visually responsive to sex traits or mainly because the media shapes men's preferences with sexualized women?
It's both, but biology plays a much bigger role in this than culture does.
Evolutionarily, men have evolved to mate with the maximum amount of females to "spread their seed". Women, on the other hand, have evolved to choose wisely, because a...
...child is a huge investment on their part. A man can always leave a child and mate with someone else, but women have evolved to be more nurturing towards their offspring and to raise them to adolescence.
So, back to physical appearance.
Men look for women with wide hips, an ample bosom, and a curvaceous body in general because that maximizes the probability that their offspring will be birthed. Wide vaginal cavities and ample milk for the baby!
Women, however, look for men that will support them in raising their child. Looks on a man are not as important because the physical characteristics will not affect the baby's birth.
What matters most is whether they stick around and help out.
I think it's a mix of both. Though there may be a small propensity for men to be more receptive of sex traits, the way we are socialized inclines us to be even more so. This goes for most other gender roles and stereotypes.
My guess is that men are typically more shallow because biologically men didn't have to worry as much about commitment since they could have more offspring. Then media uses this as bait to attract audiences magnifying it in our culture.
I think preference is built in though and mostly biological.
Maybe biology drives culture.
Ya, it is both. And media does have a large role.