If you want fast removal a 400 grit flap wheel beats a grinding disk hands down for material removal speed. problem is they are twice the price.
+1Personal preference here, I use 60 grit fibre disks on a flexible backing pad. They don't gouge the metal like a grinding disk but they rip weld down really fast and once you have bought the backing pad for about £5 the disks can be bought cheap. I bought a hundred on ebay for £10 plus post and they have lasted years.
They are better than oxide fibre discs, but you should try 3M Cubitron Discs.I prefer the blue zirconia discs ,when I can get them