From what I saw Cosmic has a lot of potential and looks pretty sleek too, right now I'm using KDE it's a great desktop, but now that I have a second monitor it randomly crashes on me, I think I'll switch to Cosmic when it reaches beta.
Depends on what you want to do I guess. I'd rather have a clean desktop that cannot accumulate clutter like in windows where applications add shortcuts to the desktop automatically which you then have to remove manually.