For the CW the best choise is a fin that give you a constant speed with the minor energy-consuming.
In spearfishing there are a lot of different situation, waves, steam, fishes.... In this case you need a fin that has a bigger employment range, and not just a specific one.
Mustang 80 is good choise for CW Apnea, but not for spearfishing.
Mustang 25/30/40 or Flap 25/30/40 are a good choise for spearfishing or normal use, not specific for Apnea.
I hope this can help you.
In you case, I suggest you to try Mustang 80 or Fuego VGR 25.
Ciao,
Natalia
