I use QuArK 6.5 alpha 8 for Q2. It's pretty good, has lots of features (most of them work) but it can be a bit cumbersome at times. It's not the newest version of Quark, but it has features that they changed since and which I prefer (multiple styles of 3d preview window at the push of a button)to use that, here's what you'll need:http://sourceforge.net/project/downloading.php?group_id=1181&use_mirror=superb-east&filename=quark-win32-6.5.0alpha8.exe&88210568http://dervish.tastyspleen.net/files/buildutils.ziphttp://dervish.tastyspleen.net/files/Quark%20setup.pdfThat will get you all the way through compiling your first sample map..I've also heard good things about Tread3d and GTK radiant.A lot of people seem to prefer GTK radiant once they have some experience with it, and if you're going to map for newer quake games it's a must.
never used anything but worldcraft
Several Quake2 veterans prefer the old QeRadiant builds. But those are Windows-only, and don't support many other titles. If you're interested in newer flavors of Radiant, there are quite a few choices. There are the now dated GtkRadiant 1.4 and 1.5 builds from SPOG, which are available on most platforms if you can hunt them down. There are what some consider significant UI differences between 1.4 and 1.5, but overall functionality is basically comparable. From there, the 1.4 branch has been forked into the version that id Software is currently maintaining for Quake Live. It's called ZeroRadiant (as Quake Live was going to be called Quake Zero), or also GtkRadiant 1.6. And the current incarnation of the 1.5 branch is NetRadiant, which is being maintained by divVerent of the Nexuiz team.It looks something like this: QeRadiant | GtkRadiant 1.4 | GtkRadiant 1.5 GtkRadaint 1.6 | NetRadiantFor Quake2World, our team uses Ingar's build of NetRadiant:http://ingar.satgnu.net/gtkradiant/index.html
Radiant 1.5 used to crash for me quite often years ago, but that was an older release. I've had NetRadiant running for days on end without issue in the past year.