I'd struggle to choose between them as both are pretty different and appeal to different aspects of my personality. My love of science and the Cranstonian exhibit, and my love of excellent suits and people drinking martinis/ retro America. Also Jon Hamm is awesome.
All I know about Mad Men is that buddy-whats-his-face cheats on just about everyone, the motif in general doesn't do anything for me. Breaking Bad has a much more interesting dynamic and the characters are so well fleshed out that even when you hate a character you can still sympathize with them to a degree. Plus the Pizza Toss, you won't get that from Mad Men.
I think Mad Men is the better of the two i like breaking bad but mad mens charicters are so good and they do the whole 60's thing really well with historic events playing out like the Cuban missile crisis and the Kennedy assassination in the show and charicters comeing to the realization that the world is changing. that show is also the reason i cut my hair i use to have long hair now i keep short - most direct impact a TV show has ever had on my life.
In my opinion they are the best shows on tv, right up there with the Simpsons. Also it sucks that your not getting AMC Gabriel, but I live in Scotland so not only do I not have AMC theres basically fuck all on tv compared to the US. Mad men gets broadcast usually at like 3am and breaking bad is around 2 seasons and 2 years behind the US, so i resort to using the internet.