If you want to go that way, then manage your time, because sanding it can make it go warm and crack. You might want to use wet sandpapers after a point with extra water in the glass and also having to stop from time to time to let it cool down (ask me how I know) and not crack!!!Okay, I would prefer the glass, because it can handle more strikes from rocks. Someone has taken my lights apart before, there is red engine silicone as an evidense.I think that I can handle the sanding, it will take some mental lubrication and time.
I will still suggest the acrylic one, even if it can get chips from stones, as it is easire to replace it from another cheap china led headlight.