Question: Difference in Lift only vs double floor?

So I’m fairly certain I’ve asked this before but I’ve totally forgot. I’ve got 50 classes under my belt now but have never done a double floor. I’ve done probably close to 10 lift only classes and I enjoy those, but what is the difference between lift only classes and just doing a double floor in a regular class? I realize many studios don’t have lift only rooms, but my home studio does.