The Phillips Xtreme +xxx bulbs have smaller, tighter wound, more precisely located filament(s) within the bulb, for better focus.
The blue coating, is unfortunate, in my opinion, but I also care more about function than fashion.
Tungsram has a +120 H4 bulb without the blue coating.
It's a bit time consuming to scrape off, and perhaps dangerous as the bulb is under considerable pressure. Take precautions if attempting. I used 70% IPA on Qtip to clean off the scarpings and act like a lubricant as well. Perhaps it helps soften it too.
I'd think if I compromised the glass in the process, it would have already blown up.
When they do fail I am getting the Phillips Xtreme h4 racing vision +200, and removing the blue coating, unless something better has become available by then.
Another member here has used a aluminum polish to remove the blue coating.
Removing the blue coating likely has them putting out 'illegal' amounts of lumens as they a have to fall within a range of output with the coating.
Scroll down to page 6 in the following link:
'What about light loss due to filtration"