XO3 vs T3: I have absolutely no idea. Maybe individual LED variations, maybe the batteries were not exactly the same charging status, maybe slightly different position of the optics (I have NOT observed any lens rattle with any of my Inovas, as other people incl. flashlightreviews have reported). I have both the T3 and XO3, and have compared them side by side with fresh Surefire batteries (batteries were from the same batch). Beams look indentical to me. There's only a slight tint variation (but with this we have to live, I guess). Unfortunately, I didn't had a lux meter at the time. Maybe when I change batteries the next time...