Cinema 4D or ZBrush starting human figure modeling

I have done 3D modeling in the past, which includes heads, hands, and lots of non-organic. But I would like to begin to learn how to make an entire human form. I am having Ballistic "Character Modeling" and the 3D World 105 'Body Shop'. For books, I only have "3-D Human Modeling and Animation", which was later found to be a bad resource.

Cinema 4D or ZBrush 3.1 which will be better. I am aware that the base mesh can be done in Cinema 4D, but is ZBrush a good direction to go in detail and fine sculpting to match the target reference? I hear good things about it, but do not want to invest money and time if it can not be instrumental in the workflow.

Zbrush is such a powerful tool; I wouldn’t want to go back to simply modeling with polygons all the time. If you have some experience with edge loops and have studied anatomy you owe it to yourself to try Zbrush. In my opinion, you shouldn't rush into sculpting if you are just starting to get familiar with anatomy and edge loops, that don’t mean you cannot have fun with sculpting but take time to perfect your skills in a traditional 3D package.

Zbrush will make detailing high poly meshes a breeze, it is like sculpting with virtual clay, if you are serious about Zbrush I will recommend buying a wacom tablet according to me it is the cheapest one. I have not found a complete edge loop tutorial for humans. I learned edge loops by creating heads and the technique can be applied to any object you can think of, including anatomy.

What you want to do primarily is to learn the tools in C4D, it is the most basic thing you can start with. I could hardly use 3D max when I started until I found a tutorial on the tools themselves. Max and most 3D software has an insane amount of useless stuff, if you just focus on modeling. Once you have learned or trained with the tools you will be able to transfer most of the tutorials for your package, unless it is an application specific task.

I will suggest you to stay away from the ZBrush because the latest version does not support the displacement with not ETA for the fix. After saying this I want to confess that I am having ZBrush 3 and I love the way Zbrush feels when sculpting. Currently ZBrush is having more features if compared to Mudbox but it can change with the release of the latest version. So it totally depends on you whether to go for Zbrush or wait for the latest version of Cinema 4D

I have not used Mudbox but I leaning towards it just because of the intuitive user interface and I think Autodesk will be superior making regular releases, but the price of Mudbox is steeper. Autodesk has just released the Mac version and a demo is supposed to be forthcoming.
I will suggest you to try the demos and hang out in their respective forums before you decide anything.

The Cinema 4D tools are known to me, which I have used them - just not as much has recently been more involved in plugin development. It would be more a matter of reacquaintence than anything. My concern, as you noted, is "application-specific tasks. Spending $ 50-80 on a tutorial, and then being stopped in your tracks because that would be an unfortunate expenditure of time and money.