Go for the cap marvel. Personally I had a rank 5 four star Corvus early on and he immensely helped me. But granted I didn’t have any good five stars at the time. I would say that cmm is pretty much on the same level as Corvus, maybe just a tad worse depending on the circumstances but is still amazing. Soon enough five stars will probably become more relevant to you and you will be happy that you ranked her up over Corvus. Hope this helps!
CMM, if you can get her awakened from trifts as well her indestructible will also be so useful for the collector