Less wattage is needed for lenses masked out for arrows, etc. The baked on black enamel tends to heat up the lens. Thats why your plastic lens says "100 Watt If Masked". No plastic lenses are designed for long term heat regardless if theres a 150 Watt or 50 Watt. If its on long enough to get hot the plastic will be affected.
Older LED traffic signals had the most color differences because of the experimentations with ITE and the MUTCD to get it close to the original incandescent color. Most modern LEDs by good brands (Dialight, GE, Leotek and EOI) are very close to the original lamps. Fade out isn't a concern in the "real world" ...safety is.
As for glass reflectors. Those were the best for incandescent light output hands down. My 65 year old Eaglelux head still has its original glass with minimal spotting. Glass is still available (and was required for signals in New York City prior to the LED revolution)