Kirika is correct however there are a couple things you also need to look at. IIRC tanks tend to prefer weapons with crit and det on them, and meld direct hit where they can (minus warrior). DRK relic has crit and capped tenacity which is generally unwanted.
MCH stat priority is crit > det > dhit, and their relic is crit with capped det. From a pure stat perspective the MCH weapon is better overall for the job, but there’s nothing stopping you from getting both weapons. Also to note with DRK you want some skill speed to get your 5 hits in under delirium.

In essence, do you play DRK or MCH more? Get the weapon for whichever you play most then work towards the other one.