GAW, or galvanized wire is kinda bad. Well, the most annoying thing is that your rodent's pee will stick to it (almost like it was absorbed) and it is a really hard smell to get rid of.
PVC coated wire is alot better but if your rat is a chewer, they may gnaw off this coating. If you get a Martins cage, I hear they will replace them.
The best is the Powdercoat wire. This is an option that you can ask for. I love the ferret Martin's cages but they can't powdercoat the large ones because the cages are too large to get to the factory that does the powdercoating.
Hope this helps.
