Well...
Dragon, MG2, UOL those are your top 3 choices for map CREATION an they all work for POl (if memory serves) Worldforge is mean't more for EDITING after the map is compiled and almost ready to go ingame.
There is a WF(POL) edition out there also with a few extra tweaks in it.
Dragon is tried an true, been around for some time w/plenty of support available. You only need 1 BMP file to compile, but have limited terrain and altitude options.
MG2 is much newer w/more options available. The color tables are more in depth, esp on the altitude side. You can really get some much smoother topography befor you ever get to the WF edit stage. downside, 2 BMP's to co-ordinate terrain and altitude. Also, some of the transitions aren't 100% complete, but all in all its a better tool then Dragon, IMHO.
UOL is somewhere in between the two. Lots of support (over at
www.orbsydia.ca) but still need 2 BMP's and the transitions are only 2-way, not 3way like some of MG2 has.
WorldForge ... once you get the map set as you like, use this to go in an "polish". No matter what tool you use to create the map with, you will always have a few mechanical things go wrong. WF has ALL the textures available to it, where the 3 map creators do NOT. So you can go back and manually change some textures and altitudes. this tool is incredibly slower than using the creation tools. So tweak an tweak an tweak again in your BMP's BEFOR you move on to the WF final edit stage.
IF you have the luxury of dual screens... You can have the map open in your test server on one screen, with the map BMP in adobe/photoshop on the other. Then you can walk the map and make edits all at the same time. very quick an exacting way to go after those little spots that just dont look right.
Hope that helps.
Pal