Here are a few reasons:
1. Mograph module. It’s awesome for broadcast graphics and ‘motion graphic’ type stuff. Just check out some of the vids and tuts on youtube. You can build up complex animation in seconds. It’s all parameter based so it feels like you are working with an audio synth or something.. just tweaking parameters and building stuff up in a non-destructive, modular way.
2. Hair and Clothilde. Get your basic set up complete in no time, all works really fast and responsively. I used to use Max and this kind of stuff was a head ache, but in c4d it’s much more fun to use.
3. Advanced Render. I’m not a render expert, but I know that this module makes my stuff look great even on default settings. Fast too.
4. Ability to export a .AEC file from C4D and open it in after effects. With this tool you can import your c4D camera animation data in to AE. Also you can add a tag to objects and they show in up AE as Nulls. So say you wanted to model an aerosol can but wanted to make the particles in AE, you just put a Null on the nozzel and then in AE you hook up your particle birth point to be parented to the nozzle null.
Also the object buffer / multi pas rendering works comes into AE nicely.
There must be a million other reasons.. I have had a little play with the rigging system (mocha) and it seems really good and a lot easier to use than other stuff I’ve tried.