I agree with byc.
Devil Dino is fun, but he really won't be featured again until the anniversary next year.
Prof. X is the only 4* I will deliberately not champ. I will always keep his blue so that it does at least 1 point less damage than the higher of GSBW's purple or SW's purple.
If you don't have another use for the ISO yet, hang on to it, because you will need it in the future.