Though it's kind of getting an OT discussion I think the problem with max is that optimization and entity placement is something that happens in the engine.
When working with Hammer i block out a level and have direct access to the manual optimization the engine bases on and can place my entities directly in the source-file and then render it up for the engine. When doing the stuff in max (or any other 3D-App) I will not have this full control. It seems to be the "ethical-question" - do I want to create a game by hand - completely from intro to extro or may i do a crysis/oblivion game where i can place 24.387 trees in a pre-baked terrain and can randomize them or do i do the classical console-title with pre-done art assets in relatevely closed levels with teleport in and teleport out - this is where max seems to work best. As in my personal opinion games like Half-Life 2 with extending levels (reach the end of the map and start at the exactly same point in the next map) and handmade enviroment I stick to the brush-your-map-method though i can see it may be usefull for other kinds of games to have everything done in max and just set it into a global heightmap (especally then using a non-bsp renderpath)
