For black, between QGD and Slav/Semi-slav, which do you prefer and why? I am trying to understand what is appealing on both sides and why you make the tradeoff of potentially blocking in the your light square bishop. Personally, I respond with the Nimzo Indian as black, and when playing as white I hope for QGA or Catalan.

Showed up in my feed on another site.

I'm assuming it's expecting Qxb5, Nxc7+ with a royal fork. But what's stopping c6 or Nc6 instead, keeping the black Queen in a position to protect c7?