Even looking at the example, I’m not sure about what you mean with “tilemap” and how you want to use WM’s output as a tilemap.
I can tell you WM can “slice” your heightmap in 32x32px output images (as well as render 32x32px whole heightmaps) and can achieve very nice textures effects. But then my imagination cant go any further and guess how you’d use them as a tilemap…
Anyway I’ve used both GC and WM, although I’ve left the former for the latter almost as soon as I’ve recognized some GC’s features as a limitation to my needs. GC has very nice erosion effects with previews that can give you a quick and reliable example of what you’re going to achieve. On the other hand, though, I’ve struggled a lot to understand most of its parameters. Also, I’ve never tried to use GC’s texturing features, but it seems most of the gallery pictures are a result of GC+Terragen2 while WM can achieve results like this one (posted by QuantumTheory on these same forums).
Now I could make a whole list of the pros and cons of WM, but I’m still not sure about what you’re looking for.
What about telling us what kind of workflow is involved in making a tilemap? This would help us a lot to understand what kind of tools and features you need and what software best fits you.