I have a couple of Surefire incandescents and have been reading about the Fenix LEDs on this forum. Is a Fenix P3d Premium 100 really twice as bright as a Surefire 9p and over 3 times as bright as a Surefire E2D??
Well you have to first compare the lumens out the front. From what I understand, Surefire lists lumens out the front, while Fenix lists lumens from the bulb, not taking into account loss from reflector and the window, etc. The general rule of thumb is to multiply the Fenix lumens by 0.65 and you'll get pretty close to what's coming out the front.
Also, suppose you have two flashlights with the exact same light source, reflector, window, etc - but one is rated 200 lumens while the first is 100. Some people may list this as the 200 lumen one is 2x brigher, but to the human eye it only appears a little brighter, certainly not twice as bright. This is because the human eye perceives light logarithmically. I'm not exactly sure on the numbers, but I heard somewhere that squaring the lumens will double the perceived light. But again, I'm not sure so don't quote me on those numbers...
Short answer... no the P3D won't appear twice as bright as the 9P or three times as bright as the E2D. It will certainly appear a little brighter... but not twice as bright. Actually I don't think it would even appear that much brighter than the P90 LA since it's much more of a thrower.