I'm going to buy my first Dremel and am not sure if I should buy the cordless (8200, 12v lithium ion) or corded (4000) version. They are basically the same price and I will probably very rarely use ...

Are you using the standard little red disks, the fiberglass reinforced, or the metal? I think they're all called "reinforced". It does take some practice to not waste disks, the first time I tried ...