I personally did the Fetch Quests just to hear/read the side conversations. Some of them is literally a knee-slapper. Like the one where Father Nier originally was going to use Weiss as tinder. Or the one where Father Nier got duped into catching a son from running away from his own family. --- NIER
ROF ---Combat system can be a hit or miss for some players. THe combat system is presented as it is right at the very beginning. Nothing much changes, at least superficially. The main meat is in the customisation of guns. ---THe story is quite sparse and not very direct. You're not showed everything outright. Sometimes talking to NPCs give you clues/forshadows about the pasts of our characters. ---My main complaint is that the dungeons/battlefields can be quite dull. The other locales however have a very good feel to them. ---The many costumes are fun if you like customising the appearances of characters. ---Quite a bit to do but everything weighs on the battle system. If you hate it then the game is pratically a no no for you.
NIER ---Good story/world. ---Many side quests but these can be annoying. ---The level designs are quite good. ---Graphics can be a bit dull and some people might not like it. ---People have said that it does many things well and there's variety but nothing really stands out. The game is good in the way that everything is somewhat sound. ---Combat might be shallow for people expecting more.
I view RoF and Nier as complete opposites. Nier has a great story with some considerable depth and great, well fleshed out characters, though it has unimpressive graphics and most of the gameplay seems uninspired. Resonance of Fate is completely superficial, it's all about the flashy battle system, the visuals and dressing your character up, it has irritating banter between the shallow cast and pretty much every story mission for the first 10 or so chapters would be considered a side-quest by any other RPG - not to say it's a bad game, but it's not a story heavy RPG and its pretty obvious why the battle system puts some people off.
If you want a good story that will probably last 25 hours with all the endings or 60+ if you do everything then go with Nier, if you don't care about story and characters and you want a pretty/flashy looking RPG that will last a lot longer go with RoF.
Personally, (if you couldn't tell already) I didn't really enjoy Resonance of Fate, I found it to be a disappointment, for all its flaws though I loved Nier.