There's no reason to compare Nier to Final Fantasy 13
I suppose, but any game that comes out around the same time become instantly compared, in concern for the gamer's $$.
Pretty much everything that hell snake says.
If there is one thing worth comparing FF13 and Nier; you're at least not limited to a battle system as your sole means for entertainment. And "quests" don't involve battles and item gathering *from* those battle. Fortunately, Nier is much more open-concept.
But hell, if you don't want to compare FF13 and Nier. Compare it to Odin Sphere; where battle and (brief) customizations make the entire game.
If you're asking whether or not you should get the game, consider the following:Nier essentially lacks what FF13 has, and vice versa.
Without going into detail (it's 3am in Canada), there's two reasons why...
FF13 is polished; Nier ain't.
FF13 is linear; Nier isn't
FF13 has very little replay value (to each his own), Nier offers several endings
Eitherway, I'm enjoying the game a lot. =)