I would recommend a heali-bo first. The dmg is not too surprisingly awesome for a dps-bo, I have a rank 10 one atm, hes good but not crazy good. I find that if I'm mobbing and sorts, a healie-bo is much much better and since your a BLM, you can already put out a good amount of dmg so having a heali-bo to keep you alive while SB'ing and etc would be much better.

However this is a recommendation based off my own use of the chocobo. Others may have a different input.