There are two different wall thicknesses:
RAL Class A: Wall thickness 2.9 mm +/- 0.2 mm
RAL Class B: Wall thickness 2.7 mm +/- 0.2 mm
Schüco SI 82 is delivered exclusively in RAL B.
Schüco CT 70 is partially available in RAL A and RAL B.
Schüco Living is manufactured exclusively in RAL B.
Basically no quality differences are measurable, all profiles are RAL tested.
For more information, see the Schüco KS system overview. Profiles marked with "Euroline", correspond to RAL B.