It's many years since I dabbled with quake based game level design (rtcw, sof2) and back then I used Worldcraft (now Hammer). From the video, it looks like Trenchbroom is a fair bit more simplistic, what is the benefit of this over Hammer?
I've been using Hammer since the Worldcraft 3 days, it took less than an hour
of using TrenchBroom to know I'll never go back to Hammer or JACK.
It just works. The overall modelling workflow is much more efficient, it's well
designed, linked groups is a killer feature, it doesn't crash for no reason and
when it does crash you can submit an issue and get it fixed in a day (or fix it
yourself, it's FOSS), CSG (e.g. the carve tool) produces sane geometry in a few
milliseconds instead of crashing after a 20s freeze.
It also runs smooth and fast whereas hammer stutters all the time and feels
like it renders its viewports and UI at 20 fps.
The apparent simplicity is a feature in itself, not a lack of functionality.
Older editors rely more on the axial views. Trenchbroom has much better tools for modeling right in the main 3D window. I think what happened here is that over time, people figured out better ways to handle the UI for modeling right in a 3D view, and it became so good that we ditched the axial views most of the time. Trenchboom got rid of the axial views because users didn’t want the axial views any more—and it got more UI improvements for working directly in the camera view.
TrenchBroom was built from the ground-up for 3D editing. You don't need to use the 2D grid view unless you want to. It looks more "simplistic" because many actions are now performed directly via the mouse in 3D.
