There is no doubt about it, Quill 3D is good, but fiddly compared to Max and as you have Max already you should not consider another, simpler package.
I would disagree. Max is not really designed as a level builder . It is much easier to create a 3d level for a game using a dedicated level builder like Quill3d which with its entity and static mesh placement and portalling system - its anything but fiddly - you just export your level as 1 .b3d with all its lighting,static mesh placement and visibility all included - how fiddly can that be compared to using Max and the .b3d pipeline. And there's no need to purchase any additional app like UU or Gile[s] even though they are very good and useful apps in their own right.