Brownie helps you deal more damage, therefore deal higher crits as well. Don't know by how much those crits get stronger but you won't always crit and you'll end up dealing more damage overall by increasing your base damage.
I would choose Brownie. The TDD decreases affects both your normal and critical hits.
If you're a Crit Dragoon Spear, the Fat Panda's buff would be nice. If you don't have a high Crit Rate, it's not exactly that helpful.