Go with the Prometheus 6.03...they are harder on the Rockwell scale (harder, and will stay truer) and have a slightly higher outer diameter (along with a decent crater cut for a nice sound).
You have to clean them a lot because gunk builds no matter what, dirt and grime and other stuff, but instead of being a .09mm gap like on your stock 6.08 barrel, it's a .04mm gap, which means there's a lot less room, and that means the more gunk, the more the bb will be affected.
Don't go below 6.03 because it'd be stupid. Just don't use shitty BBs and there won't be any problems.
P.S. I have no idea what kind of BB would "shave off" in the barrel.
That would be a big fuckin' bb.