Everyone say it with me now:
JC👏Staff👏butchers👏yet👏another👏classic👏light👏novel👏series
But in all seriousness: Index and DAL follow similar plot structures. Each season is split into multiple "arcs" which follow the protagonist as he tries to save every girl he comes across and gets them to join his ever-growing harem. The protagonist of both shows are your standard typical anime "nice guy" guy who is always morally right and will always try to come up with ways to solve every problem while trying to save EVERYONE, including those that are trying to kill him.
Date A Live III and Toaru Majutsu no Index III were the long-waited sequels to
two classic and beloved anime. However, due to many nonsensical decisions and "lack of skill" from the people working on both shows, they both ended up being quite disappointing for most fans of the series. The art quality fluctuates between fine, barely passable and straight up terrible at random moments, the animations are either extremely lazy or virtually non-existent and the story is "adapted" in such a way that makes it almost impossible to understand a lot of what is happening in either series without knowledge from the source material. JC Staff skips through content that should have been at least 5 episodes long in three, two, sometimes ONE episode... which is completely illogical no matter how you put it. In no situation should you be allowed to cram a 320 page long book into a 23 minute long anime episode.
In any case, if you DID genuinely love the third season of DAL or Index, and none of the issues mentioned above bothered you at all, then I highly recommend checking out the other, because there's a huge chance you can end up loving the that too. And once you get passed all the terrible production issues, they really are very enjoyable shows :D read more 
