Keep this inner ability as a BM or keep going?

Don't get your hopes high.
400~ Circulators no boss dmg.
The best tip that every player who knows this pain is,
When you get something GOOD, STICK TO IT.

See, the thing is he can still try to get more if he wants to change. Once Unlimited hits though he'll have to use cash for that same ability if he wants it to go up to Legendary rank so it's not so clear-cut.