In a general sense, mass-market consumer bulbs should be all pretty much the same. Yes, you'll have differences in brightness, hotspot and longevity but these differences are relatively minor. By this, I mean that these bulbs are all designed for the massive percentage of "average" drive and performance situations. Typically 1 amp or less of current. Let's face it, when they sell you a 3.8V bulb, the assumption is that you will most likely drive it with 3 alkaline cells.
Once you start into the world of high performance incandescent lighting though, the horizon opens wide. For example, Welch Allyn, a manufacturer of HO bulbs used by more than a few CPF members manufactures the WA01112. This is a 6V, 1A bulb that makes 119 lumens with a life of 50 hours. On the other end, they make the WA01111, a 6V, 3.35A bulb which makes 465 lumens and yet lasts for 100 hours.
Wilkey