The "best" copper wire for bonsai is Jim Gremel's. He prices his wire by weight. Adams prices his by the foot. I'm sure the smart folks around here could figure out whose wire is the cheapest...
When you buy from Gremel, his spools are larger. Both in being a physically larger spool, and each spool has more in it than an Adams spool. But it costs more.
I use a lot of copper, so I like having the larger spools. But, if you don't use a lot, Adams wire would mean you can have some copper on hand without having a lot of money tied up in your copper inventory.
Both sell good wire. They both sell good trees, too!