There was a thread that figured out how to price compare Adams and Gremel. If my memory is correct, Gremel's came out less per foot. But Gremel's spools are larger in diameter, and heavier than Adams.
So, maybe if you want some wire, but don't need a lot, buy from Adams. If you use a lot of copper, it's more economical to buy from Gremel.
Gremel also offers free shipping if your order is over a certain weight or amount. (Can't remember which the discount is based on.)
I've "talked wire" with Gremel and Adams. Gremel tells me there are a couple of wholesalers of copper, and the quality varies between them. One is purer copper than the other. I think he says it costs a little more. But it's the one he gets.
Neither of these guys are spring chickens. I usually buy two rolls of every size. On my next order, I think I'll double or triple that. (I don't use very much 18, and even less 20, and never used 22 even though I have a roll.
I mostly style JBP. The sizes I use most are 14 and 16. Never 18.
On JWP, I'll use some 18, nothing finer than that.
The 20s are good for super detail wiring of juniper, and some shohin. I once wired a shohin zelkova. Had to use tweezers! I felt like I was making a ship in a bottle!