If I were you and...

- I wanted to push new content by joining a static group: I would go SMN
BECAUSE: SMNs do have raid utility and have special applications. It is also going to be extremely rare to find a vacant BRD spot in a good static, as BRDs are usually one of the better players or the leader, as they tend to handle specialty mechanics most often.

- I wanted to do older content that has the echo applied or has been deciphered so much that it is very easy: I would go BRD
BECAUSE: Stacking 4 BRDs on echo-applied content or easy content makes it easy mode. If you remove the DPS checks from things like T8 or Ifrit/Titan X etc, BRDs become the ultimate flexibility tool because they are hard to kill and supply songs to the party that refresh resources that cannot be applied by other any class.