Sadness be gone! Though depressed people are scattered across the world, there are those from a parallel world that are here to help. Known as Juuden-chan, these busty ladies use their special powers to charge up the mentally dejected and earn a living in the process. Aresta and Plug are two Juuden-chan who, while performing their duties, discover a boy named Sento. However, he’s different than most humans: unlike the rest of mankind, Sento can actually see them. Now, in addition to their duties helping the depressed, Plug and Aresta must juggle watching their favorite hentai, getting into trouble, and being hit by Sento’s bat which causes them to urinate and become aroused. Perversions abound for these two rubber suit-wearing, otherworldly beauties!
Nanoha used to be a normal grade school student until one day she found a ferret in the woods -- but he's no ordinary ferret! His name is Yuuno, he hails from another world, and he needs Nanoha’s help to complete his mission: to capture the Jewel Seeds (mysterious stones that imbue their wielder with great power) that fell to Earth. Along with Yuuno, Nanoha must now collect the Seeds and protect her world, but she isn’t alone. A rival is also trying to collect the Seeds for an unknown purpose, and only Nanoha has the power to stop her…
Both are magical girls shows. Nanoha is basically what happens if you reduce the amount of ecchi in Twin angel and add a deeper more well thought out plot with questionable morallity and deception.
Both series feature girls trying to protect their world, their friends and their family all with gracious amounts of fan-service and some melodrama. Symphogear however has deeper storyarcs and more character exploration with far fewer light hearted moments.