The engine and training features are better ... though I wouldn't break the bank on it because all Fritz product increments beyond 9.0 appear to be mere additions of more bells and whistles rather than day to day stuff you'll be using (analysis, training modes etc.)
Edit: From what I'm reading, Fritz 12 changed their GUI ... so that's bound to lead to more exasperation than acceptance if you've been perfectly fine with the existing Interface. (I'm one of those people who want to chokeslam the creators of the new Micro$oft ribbon interface paradigm)
I have Fritz 9. Is there anything in Fritz 12 that I would need that is not in 9?