Depends on what you prioritize that day.
Normal bonus stages easily offer the best life crystals per stamina IIRC (10 crystals for 80 stamina for the advanced one) as well as guaranteed manyu/ampies. But they don't offer event currency or progression on the event stage dailies if you care about the equipment upgrade materials.

Event bonus stages typically offer the best event currency per stamina, but no life crystals or progression on the event stage dailies. Also, how much 'better' they are at helping you clear the event varies wildly depending on the event type. There's at least one or two types for which you're better off never doing them IIRC.

Figure out what you want to do that day and play accordingly.