The differences are obvious: color tone, placement of the ruffles. But are they different enough that you'd choose the silk version for more than twice the price of the polyester one?
I happen to think either one would look nice on the right body type. Those of us with girls over a B cup may want to steer clear of them both. They both look pretty casual, and while polyester can be GROSS, silk can be hard to wear in the heat. Which do you like? One, both, neither?