Check caliper first for brand
I'd check the brand of caliper that MB installed on my car first and match like brands if possible. I installed Balo discs on my wifes 300E and they looked great coming out of the box and have performed well since installation about a month ago. If you want to know if the hardness is different between brands, I can't tell you that info, probably no one else can either unless they're into metalurgy. I do know that the small cross hatched design in my rear disc are still there after almost a thousand miles on them and the Teves pads seem to perform great as compared to the grooved rotors they replaced and the bare minimum pads that still remained. Balo does make a great disc from a users point of view.
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan