I have some familiarity with glass now and can tell you this. If the glass has the MB star on it that means it came through MB channels (i.e. from a dealer - not necessarily installed by a dealer as most don't do glass but they supply the glass to installers). Then there is glass which is supposedly identical but doesn't have the star, which is the equivalent of buying aftermarket parts (if you buy a Bosch starter at PepBoys instead of a Bosch starter at the MB dealer it will not have the MB part number on it but is probably otherwise supposedly identical). I say supposedly identical because my dealer is now blaming an operational problem on one of my side windows in our 2004 C240 on "aftermarket glass" even though it is Pilkinton and has the same ID numbers on it as all of the other windows...it has no star and they say the reason my window won't stay in the closed position is because the glass is "incorrect" and needs to be replaced with MB glass ($300) so they can repair the fault. I bought the car second hand and don't know the history of it but assumed the operational fault would be fixed under warranty
In the glass business there is "premium" and "standard" quality. Apparently PPG is standard quality. Sekurit and Pilkinton are "premium" quality. Nobody has been able to tell me the difference except for price. I can tell you that based upon my own personal experience that none of the MB windshields I have ever had held up very well to road hazards. MB seems to prescribe a "softer glass" that easily gets "sandblasted" with lots of pits which become noticable in as few as 30K miles. I have seen this in all three brands of glass. Also, the PPG windshield I have in my E300 has 5 stone chips in it. I've owned lots of other brands of cars and never experienced as much disatisfaction with windshields as I have with MB's. The only saving grace is that it is not that expensive to replace them and many times insurance covers it even if it is just pitting because the insurance companies want you to be able to see well and not be sued when you plow into another car and the other driver's lawyer sees your windshield is covered in pits and chips and you are open to liability because of it.