Either workflow is fine.
It all really depends on what you want to get out of the program.
I personally use zbrush as an artists tool to build things from the ground up, but a lot of people use zbrush as a detailing tool.
Sometimes it is faster to build something in a traditional 3d app. Sometimes Zbrush wins, so it all really depends.
Then…what is the final goal of the piece?
game model?
animation piece?
still image?
statue/3d print?
Find some 3d artist that you like, find out how their workflow is, try it out, and see if it works for you.
The main reason Zbrush is the best application on the planet (in my opinion) is that it lets you work the way you want to work.