I'm using zbrush and all i can say is this: pure fun!
I use Cinema 4D to create a low polygon model, unwrap it and then import it into zbrush. I then create a high poly model (damn this is so much fun!), let zbrush do the normal-/heightmaps (1 click and you're set), export it as obj and have fun

However when exporting models from c4d, make sure there are:
1. no ngons!
2. no triangulated polygons!
3. everything has to consist of polygons built out of 4 vertexes (does this word even exist

)
I also tried mudbox some time ago. I fiddled around with it for like 30 minutes and then uninstalled it. Maybe zbrush really is easier, faster,prettier ... maybe i'm just used to zbrush

I'd say try both (there are trial versions of both zbrush and mudbox if i remember correct) and judge for yourself.
All i can say is that i never had any problems in using zbrush with 3dgs/tgea/lawmaker