Senki Zesshou Symphogear G

Very similar plot lines MC in both obtain a battle suit that turns her from school girl to defender of Justice or just their friends Lots of action in both by kick ass female characters  

Girls, transforms, colorful graphics... 

In both shows, magical girls from rival groups battle each other. Both anime also contain sci-fi elements. (Keep in mind they're both second seasons to their respective series) 

Both include magical girls, with cute transformations, trying to save the world from evil. Many of the characters have similar characteristics; For example Hibiki (szs gx) and Yuuna both have powerful punches along with the sense of always wanting to protect people in a heroic way 

same energy - using music to fight 

They have a similiar feeling, where their magic powers they thought were supposed to help people turn out to have a dark side they didn't know about. 

There's ALOT of Evangelion references in Symphogear, both in this seasom and the previous. Like the mecha suits that only some people can synchronize with, the mysterious threat only said weapons stand a chnce against, somewhat mad scientists. They also share the religious references, Nephilim, "berserker" mode and so on. Plus in the first season they also have an equivalent of Central Dogma, hosting an artifact that the enemy is after deep underground. I'd say this show is magical girls with a touch of NGE. It's nowhere near as philosophical and deep, but it's definitely very disturbing at times and Symphogear deals with moral questions in their own way. read more 

both show has the same number of hero and rival, 3 vs 3 Taiki was a legend before the first episode of this show, so does Kazanari Tsubasa Yuu and Yukine were previously an antagonist that had brainwashed by the main villain, and in their sequel, they both took the same role as a supporting character Tagiru (so does Gumdramon) and Hibiki are so stubborn and both have so much guts for being a main protagonist 

Symphogear G is very similar to all the Nanoha series as both share these main elements: -Girls fighting with mecha-like gear and weapons. In Nanoha the mecha element is linked to Magic while in Symphogear its linked to singing and old artifacts. Either way the result is the same badass girls fighting epic battles with technology/ mecha super abilities.  

Symphogear G is very similar to Mai Otome as both series have girls using the power of technology in order to fight evil. In Symphogear G the power comes from signing and old artifacts while in Mai Otome from a special substance that is injected in your body on the condition that you are a woman. Either way both anime are bassed on the mecha/technology elements in order to acquire power and fight. 

Symphogear g is definitely similar to Vivired opeation. Both series: -use techology based /mecha- abilities in order to fight evil. -the power of friendship goes without saying as well as the transformation sequences. All these result into epic fighting sequences. Make sure to give it try.  

both have the idea of friendship between women both involve fighting with song activated weapons, and this idea of music connecting people (and other stuff) both are train wrecks that turn out to be interesting