The Alienware x16 is thinner than the Blade 16 or Asus Zephyrus M16 and yet it's still larger and heavier because of its wider width and extended rear. Being the thinnest of the bunch evidently has its costs.https://www.notebookcheck.net/Alienware-x16-offers-175-W-TGP-graphics-while-being-thinner-than-even-the-Razer-Blade-16-but-there-are-some-caveats.727904.0.html
The Blade 16 isn't even that thin. The 15 is, but the 16 is a thin & light "rethickened", and is one of those models pretending to be thin through visual tricks like the rounded bottom corners.