Originally Posted by m3an
OEM glass is Pilkington and is very soft and chips easily. (see Euro regulations re: glass safety). A/M glass has gotten much better; if you want A/M stick with PPG/ (pittsburgh glass works) which also does alot of OEM work. Definitely inspect the glass prior to install as you'll be able to see if there's any imperfections/distortions in the glass. If the A/M glass is good, just use it. The only downside is you lose the BMW logo in the lower corner of the glass.
So, while OEM is def #1; PPG or aftermarket Pilkington, is just as good IMO.
Make sure the glass is correct with rain sensor/etc prior to install also.
+1000 There is nothing wrong with a quality aftermarket glass. Except if you want the BMW logo in the corner..and sometimes buyers look for it as a sign the car had a replacement
What I would be more concerned is getting installed properly because this glass is structural and bonded to the body.