If you want use newest software, c4. C3 does not support them, plus it is little uncertain if it can communicate with 2012 car properly. Problems with c4 is that again older cars (need of HHTWin) may be problematic if you want help someone with W202 etc, though people have been successfully installed HHTWin with those hardware too.
Many of C4 clones (I assume you are not after genuine one?) have been very crappy quality, and trouble to find good seller (installation/setup support).