It is a total crap shoot with butterflys and peppermints. I have had both (many times) and neither one is completely effective or guaranteed.
Butterflies can be an extremely difficult fish to keep for most people, even those with a lot of aiptasia. If you get one that eats it, it will most likely die from starvation once its gone as you struggle to find a food it will eat.
As far as Peps, you may end up with ornamental shrimp that dont touch the stuff just like I have had so many times.