I see people tend to go with Fractal because it's easier to mindlessly grind. With Netherreap, you have to deal with annoying mechanics. As easy as these mechanics are, it takes away time from doing damage when you are searching for the shadow and killing adds (first boss), moving totems (second boss) or killing adds while dodging tornadoes and the boss being invincible (third boss). The bosses in Fractal have extra mechanics on bosses, sure, but there really isn't a lot of time when the boss is simply 'immune'. Even though there are adds to deal with in all three bosses, you can keep damaging the boss at the same time (this coming from a SMN perspective). Also, the minion from Fractal is far cuter and (usually) worth more money depending on the server. Finally, while there are a few safe spots for big pulls in Neverreap (to avoid tornadoes), you still have to be careful and watch your surroundings. It's not as much of a mindless AoE spam grind. I wouldn't protest to doing either, but if I had to choose a mindless grind, it'd probably be Fractal.

As far as OP's situation, don't forget to do your daily hunts, daily trial, daily high level, daily expert and (possibly) daily low level if you want to. The bonuses are really nice. Also, take up on anyone's offer to run a person through either of these dungeons a first time. You get a 40 law bonus. That's one of the reasons it's sort of advantageous to queue up solo or without a full party... you could 'get lucky' and get a first timer for the bonus. My group always gets super excited when we enter and we notice someone's in a cutscene... haha. As time goes on, the likelihood of getting a newtimer is likely to decrease... so take advantage while you can. Also, that 40 bonus law applies to the 60 storyline dungeon, too (but not the trial).