I've used both.
The REDs were only good when hot, the cold braking was terrible, soft pedal and very poor brake force.
On the odd occassion you went on a good long blast and got them thoroughly hot throughout, the pedal firmed up and they were great, but that was only like <1% of the time.
Recently fitted Yellows with new discs and they are fantastic, such stopping power even from cold, firm pedal and great feel, I had to recalibrate my right foot to stop giving the passengers neck ache!
Again they need to be warm to get good stopping power above legal speeds, so don't expect wonders when charging off a motorway slip with freezing brakes, but for everyday and spirited A road driving they are great, very pleased with them.
It'll have to wait till the next trackday in spring to really test them
Obviously theres a lot of dust from running in and I haven't washed the car since fitting them so it's filthy, so can't comment on dust levels.
E63 AMG on the way