Oni returns. Raid or farm?

A summon ticket will be give per oni defeated.

farming and raids use two separate resources to complete, so there's very little reason to have to chose.
if you just don't feel like investing the time for both, its probably best to just farm currency unless the raid has an important drop.

If you are done with the 200M DP, just raid the 3 BP for event currency and gold gems. You don't need to deal the whole 6M as you will get all the drop items even if your party are defeated.