Other owners have generally suggested stainless is better -and even cheaper than (original) MB exhaust systems. Good stainless systems should not sound louder than the original, and should last longer, particularly with the short trips some of us tend to take. An important aspect is the fitting: if not installed properly, the system may touch the body of the car which will cause resonance and other problems, like those rubber donuts breaking off all the time. The original systems were welded front to back. But clamping should work also.
As for makes, the Timevalve system seems to get the best reviews in the US. I will email you seperately the posts I have gathered over the past year that concern the exhaust system, some of them are in the Technical Articles on this site as well.
Cees Klumper in Amsterdam
'69 white 280 SL automatic