Hmm. The crafted upgraded chest is better than the Ridorana one. That + diamond gun would probably be best short term. But you're right that the tsukuyomi gun isn't that bad. Diamond still wins out easily but skill speed can be problematic as you know. You arguably have a better chance of getting the gun as a direct drop though as you say. Up to you really, depends how much speed you're willing to tolerate in the short term.