I'll give you the short version. BRD is overpowered and is getting a well-deserved nerf. BLM is a bit on the high side and is also demanded for every endgame party, but probably won't be touched because it's reportedly Yoshi's favorite job. SMN is powerful, but has a few specific disadvantages (pet deaths, limited burst damage). MNK is potent except for a few nagging issues; it still shows up in raid groups very frequently. DRG is underpowered and will be buffed in 2.1.

If you want the best roll right now, go with your 50 BLM. You can reroll DRG in 2.1 if it gets buffed sufficiently. If you prefer how MNK plays, it's a fine choice as well, just beware that it requires more skill than any other DPS job.