For me, I use spaces constantly to help me organise/compartmentalise what I’m doing. It lets you group related windows, where command tab only brings you one window at a time.

One example would be if I’m working on a document that draws on others I have written. Put all three in a space and that piece of work is nicely organised.

When I have all my windows in one space I find it messy and stressful and it’s harder to find what I want.

Overall spaces are more compatible with the way I think than command tab.