We have spent countless hours in research and development of our Dura-Bulbs to make the polycarbonate Dura-Bulb and Glass versions of our bulbs to look as similar as possible to each other, but the inherent differences in material, thickness, and the fact that one is a coating (glass) and the other is the material itself diffusing the light (polycarbonate) can result in some apparent differences, especially to finely-tuned eyes or vintage lighting fanatics (a term we use lovingly, of course).
If vintage authenticity is your primary concern when purchasing bulbs, we would recommend our glass bulbs. If you are willing to forgo a little authenticity for the shatterproof and other benefits Dura-Bulbs offer, we recommend giving them a try.