The only series that I take seriously is Madoka Magica. I watch it religiously, whether subbed, dubbed, or raw, pick apart every theme and character action, try to experience everything the series has to offer, listen to the soundtrack, read the manga adaptation, read any and every piece of spin-off there is, from manga to drama CDs (waiting for someone to scan and translate Suzune Magica.) I can talk for hours about Madoka.
As for the spin-offs, The Different Story is not only my favorite Madoka spin-off, but my favorite spin-off in general (Although I guess it's more of a side story, though.) We learn more about Mami and Kyouko, and their relationship before the events of the show, but also gives us a new take on the story with Mami playing the lead role, and we are given a much deeper insight into her character. I actually quite liked Oriko Magica, despite it's messy art and other shortcomings, as I really like the idea of it, as well as the additional characters. I have my issues with Kazumi Magica, though. The story was a bit too complicated and hard to follow (Or maybe it's because by the time a new chapter came out, I more or less forget what happened previously), mostly due to the art. While it looks nice, I had a hard time following any of the action scenes, and a lot of the characters looked similar so I had trouble telling who was who. Also, as a fan, I didn't like the designs of the outfits. Madoka Magica's outfits were sleek, tame, very European-influenced, fitting in tone with the style and setting, while still being reminiscent to classic magical girl designs. Even Oriko Magica kept in tone with this. The designs in Kazumi were too flashy, showy, and didn't really fit in with the Madoka universe (And unfortunately, Suzune Magica looks like it suffers from the same problem. The main's outfit looks very similar to Black Rock Shooter's. Hopefully the story makes up for it.) A lot of elements just didn't fit into the Madoka storyline. Also, I thought the ending was fairly anticlimactic. This is probably one of the few cases where I partake in any sort of fanboy complaining (Other than Evangelion 3.0, but that's another story.)