In my heart, as a conscious fashion consumer, I feel like I should prefer silk. It's a natural, beautiful, traditional, and luxurious fabric. Obviously.
That's why I'm cynical when fast-fashion brands like ASOS announce they are banning silk from their offerings. I don't think they're doing it for altruistic reasons, but rather that they want to save money by using synthetic and semi-synthetic alternatives like polyester and rayon/viscose. The praise they get from vegans on social media is just a nice little bonus.