I'd agree to stick with the manufacturers recommendation. In general I try to use the one MB prints on the label in the drivers door jamb, unless I know the car is always heavily loaded, in which case I use the max pressure as listed in the fuel filler door.
I agree there are variables in tire construction, especially if you have an older car with new tires, BUT that hardly allows you to make the leap from the manufactuer specifications to the MAX tire pressure listed on the tires, that's quite extreme.

If for some odd reason the MAX pressure listed on the tire sidewall is LOWER than what the manufacturer recommends, then DO NOT exceed the limit on the tire under any circumstance. This is rarely the case though.

Gilly