Elemental Obi's only work on the Day/Weather they are attuned to. This is always. unless you carry every single card and every obi. I'll personally take the +7 inventory and +3 Mab at all times for my QD.
It's 3% constant damage on all QD vs 10% extra limited to 1 QD. Elemental Obis are still nice to have, but if you're in a fight where you're using multiple elements of QD, this is a lovely belt.
AND YET ANOTHER QUICK DRAW SLOT FILLED!!! YAAAY!!!
Damn, with the new gun (51 base damage) and all the new MAB shinies COR has, I'm thinking a 500 damage Quick Draw shot will start to seem like weaksauce.