I love both shows but thought the most recent seasons (season 3 for both) were there weakest. I prefer Breaking Bad of the two, but they are both great. The acting is very impressive in both, and I love the sets and atmosphere of Mad Men. I think they do both have some faults though, pacing is sometimes an issue on both shows althoughlots of times thats intentional. I think Mad Men sometimes strays too much into soap territory with on again off again relationships, and I think character motivations on Breaking Bad are somewhat suspect especially in the 3rd season.
This year my four favorite shows were 1. Lost 2. Friday Night Light 3. Mad Men 4. Breaking Bad
With Lost over with I'm not sure which show will be my favorite next year. But AMC has definitely done a great job with the first two attempts at scripted dramas, I hope their new show Rubicon is just as good.