Depends on the manufacturer I'd guess, which is why I've been looking into this. Lexus/Toyota don't make their own windshields, so it's possible that a non-OEM sourced windshield was manufactured in the same place/way and just has different branding. I haven't been able to find solid information on who the manufacturer historically has been for the LX/LC, but it seems likely that it is currently AGC.
I've heard many times that there are aftermarket options that are much worse quality than OEM. I wouldn't be surprised if this is true, but at the same time, I haven't seen any actual testing done.
My current cracked windshield is Pilkington, which is supposedly pretty good. I won't be able to do a road test comparison when I get the new one installed, but maybe I could play a frequency sweep outside and measure the volume inside. Actually that'd probably be better than a road test since it would eliminate variables related to trim and molding installation.