Most of time I chose power over frags.

First thing first, you really need to calculate if those ninja frags are worth to redeem by points. There may be other events that those are cheaper. As usual, you either ask people in the forum or look for it they will tell you if it's worth to redeem.

I've been collecting Hanzo over time though. I think that's only ninja I've been collecting other than refine.

What I like so far for this event and previous one that they both have med refine. In 2 events I've collected over 100 med refine. I like back-to-back events where you just keep collecting until Refinement event comes.