From what I remember, ClassicArcadeGraphix didn't have a very good reputation (search for their name on this site, BYOAC, and RGVAC to read about them yourself), but they had a ton of available artwork that no one else had. Then a few years ago they closed and offered their massive collection of arcade art files for sale. Some people on BYOAC organized a group buy, so they all got copies of the artwork files. Notably, MameMarquees (now known by the confusingly similar name GameOnGraphix) also bought CAG's artwork files, so his product availability shot through the roof overnight (he has the Spy Hunter CPO as well). He also has a better reputation than CAG did.
Apparently, CAG is back in business; I don't know when that happened.
Both CAG and GOG are inkjet printers.