Both are deviations from the traditional mahou shoujo format, and while Madoka is the darker of the two, Nanoha is far more accessible and appeals to a much wider audience.
Both are out of the ordinary magical girls shows targeted at a mature audience with similar protagonists who share a similar relationship. They both also have a cute design who can fool the viewer on their true nature.
Madoka is much more dark and psychedelic than Nanoha, though.
Both of them prove that it's still possible to create a mahou shoujo anime that is both original and creative. They both play with your emotions - while Nanoha just tickles them, Madoka kills them mercilessly.
Come on! Magical Girls? Kick ass girls? Yup. Both have them. But these shows are no ordinary magical girls that kids these days should watch, particularly Madoka. Be warned to get fckd up in Madoka. In a good way.
similar characters personalities,similar plot and both have a small pet that gives them power.
Rather than the typical romance series aimed at shoujo audiences, both of these series have more mature themes.
Additionally, the story gets darker with each episode progresses. There are also sci-fi themes as well as containing drama, action, and comedy (less so in later episodes).
Nontheelss, these two series are not your typical magical girl anime(s).
Both start off as generic magical girl shows before becoming drastically different. While Madoka starts becoming much darker, Nanoha focuses more and more on action. Both have almost completely female casts and a lot of yuri subtext.
Both are magical girls shows but Mahou Shoujo Madoka Magica is a much darker anime and unlike a magical girl story anyone would expect. Mahou Shoujo Lyrical Nanoha appeals better to more audience and much less serious compared to Madoka Magica. Its best if you watch both of them.
Both normal school girls came across a magical injured creature that asked for their help and it changes their life forever. Fighting to protect the people they love from dangerous beings. Unlike 'Mahou Shoujo Madoka★Magica' , 'Mahou Shoujo Lyrical Nanoha' have a longer story line, and it definitely won't disappoint you if you watched it. 'Mahou Shoujo Lyrical Nanoha' starts from the main character as a school girl to a full grown adult. This anime was the first anime I watched and I instantly fell in love with it.
You might think "these are just some uninteresting magical girl animes where they have magic and fight some monsters" but actually these 2 have a much deeper story and heavy subjects than you might have thought.
both are magical girl anime and both twist the typical magical girl genre
Nanoha is more of a warm-up on knowing about the magical girl genre before going to the real deconstructive drama of Madoka. Both are basically magical girl series that apply to a mature audience, with Nanoha having occassional fanservice and an easier-to-follow storyline and Madoka featuring a twisted, multi-layered plot.