I use both packages ...Zbrush and 3D Coat.....I find they both have their strengths and weaknesses. Zbrush is definitely a deeper package and a little harder to learn. 3D Coat is much quicker to learn and can do a great job with most things.
3D Coats Retopology tools are much faster and more user friendly than ZBrush's.
But where ZBrush packs it's best punch is that you can get more detail in HD Sculpting. So if you are making a character where you need to zoom in on the surface very close I would say to use Zbrush on that aspect of your project.
But at this point in time I wouldn't want to trade one for the other as they can be used seamlessly in a pipleline together utilizing their different strengths...
So ya....I recommend both pieces of software