It's a Hammer only contest
I am so sad about that
...I feel like I bowl out. I also started mapping with WorldCraft, but it made me a lot of errors on my maps (most caused by bad vertex manipulation).
doing it in Quark is so much easier
That is why I am using it. Vertex manipulation is not a morphe mode in it, this made me angry so many times in Hammer, because just simply cant undo moving of one vertex (must exit morphe mode to undo changes you made). And just cant create an invalid brush in Quark by vertex manipulating, rarely it can make error in your compile, but not in the building part. This means that when you move a vertex in an invalid positon the whole brush transforms to make the brush valid.
Quark is a bad level editor
laugh...
I am not saying Hammer is bad (I also use it sometimes). It has a very big advantage in texturing, but Quark has a very big advantage in creating brushes.
nothing in quark that you can do that hammer cant
That's right, but why should I spend 5 minutes on creating a stairs if I can do it in just 1. There are many usefull stuff in it, Half life RAD editor (for texture lighting), shape builders (bevel, arch, staircase maker,...), some precreated brushes (like pyramid, prisms (8-10 sides), wedge,...), advanced search (bad tex scale, find microbrushes, find thin faces,...), you can mark your selection and can make some advanced selection, for example there are options to select only brushes, only entities and everything,...there are plenty which I didn't mentioned. I am sure Quark is more advanced in creating polyhedrons.
the navigation is all weird in quark
It can be for the first time, but after a little practice you will figure out it is much more easier (for me sure).
The usage of it is optional...