Clear glass is said to absorb 10% of the light. That silicone cover wouldn't surprise me if it were a LOT more than a 10% light drop.
I know this is an old post, but wanted to chime in. I removed the silicon film.[1] I got about a 3% improvement in brightness on an 18w (100w equiv) bulb. I used a free app on my phone (beeCam light meter) to measure lux. Not a scientific test.
I just hope that film isn't some kind of UVA protection.
I removed the globe on a 9.5 (60w equiv). I plan to use these bulbs in clamp-on reflectors. In a reflector, I didn't feel the globe-less was an improvement. I couldn't compare brightness because the light was concentrated differently. The light cast on a wall showed a much more defined circle, the "cut-off" of the reflector. Looking into the light there was a much more concentrated ring reflected at me. Without the globe it might have better penetration. But, I want to have it close. I worried the harshness or concentrated reflections would create hot spots. I didn't think it was worth losing the softer, uniform light.
Not a waste though. I put it in a ceiling light which has a translucent globe. Looks perfect.
[1] Easy to do. Score the bulb surface with a razor or knife blade, then rub the cut with your finger. It rolls up like contact cement.