I'd agree with others that the white brushes are too aggresive on many carpets.
I use Gold for most of my work and find them to be essential on all domestic wool and cut pile nylons (Flotex excepted). They also do a good job on polyprop if it's not too flattened, which is when I would use the Chipmunks. I can't remember when I last used white brushes.
Brush selection is something I'll touch on tomorrow in my presentation at Wolverhampton. There are many techs who use aggresive brushes because of the soiling level. This is not necessary. You select brushes to suit the carpet, otherwise shedding and pile burst damage is inevitable.
Safe and happy cleaning

Ken