I never played TA (not a big mobile/handheld guy), but my understanding is that "regular" FFT is a much more mature story. Ivalice Chronicles is a basically 100% faithful recreation of the original, just with graphical updates, some quality of life improvements (letting you restart a battle, difficulty settings, autosaving on the world map, and autosaving during battles are the big ones--you may have heard about folks getting softlocked at a particular notorious difficulty spike in the original, but that's no longer possible), and a retranslation. The original always had a fantastically operatic political story with strong themes of class conflict, but the translation left a lot to be desired (and was borderline incoherent in some places). That's been fixed, and fixed well. War of the Lions, which was the first attempt to do something like this, added a bunch of new content. Ivalice Chronicles does not include that content: it's really just the original game, but rebuilt from the ground up for modern hardware and with a few modernizing touches. If you like this style of game, I'd say it's a must-play.