Both jobs are needed in the same amount, so it is really just up to your personal preferences.

BRD will change a lot above level 50, when you get a stance that will make you a "caster" and gives you a damage boost. Maybe level up to there and find out how that suits you and then you can decide wether you want to try out NIN more? Just a personal suggestion though. ^^

To my experiences (I am not pro as BRD/NIN, just play it from time to time in dungeons), both have a lot of OGCD skills and are quite dynamic classes, which can be a huge help for the group with buffs for increasing party damage. I think in the end it comes up to the question if you like to be a melee and run around a lot or a range who casts and therefore needs to stay for sometimes.