Sell this shoe or go for decCO?

A good question to ask is whether DCO is really that useful to you, compared to a line of %(all)stat. I will not attempt to do numbers for you because I don't know what you're starting from and what else you're hoping to get (as an alternative cubed result), but sometimes I feel that DCO is heavily overrated, unlike DSE.

If you're having this on your cannoneer, I'd also need to be enlightened by what Double Down actually does...

Hadriel

He is trying to make dec CO shoes that he can equip, cast dec CO, and then unequip. He has 140 shoes that he will be using most of the time, but yes, having dec CO will give him a pretty nice boost.