Descent had that very early 3D where everything is made out of like 8 gourmand shaded polygons and a lot is left up to the imagination. Doom's pixel art just plain looked better even though it was less technically accomplished. Quake 1 suffered from the same problem, it just didn't look as good as the previous generation. Worse, drawing those polygons was a lot to ask of the computers of that era so they generally limited themselves to a small number of enemies at once, you never got swarmed the way you did in Doom sometimes.

Also, I personally found myself getting lost and turned around way more often in Descent than I did in Doom. That last part of the mission where you had to fly back to the exit before the reactor exploded was always the hardest part.