Runtime probably won't be an issue for a weapon light, since it probably won't be on constantly. Given the same current and voltage, LEDs tend to produce more lumens than incans. However, incan light is broad spectrum light, so fewer lumens are typically required to provide the same amount of usefulness. Put another way, OTF lumens aren't what matters, unless the goal is for the light source to be seen. What matters is how much light is reflected back to the user. Typically, it requires more, sometimes much more, OTF lumens from an LED than from an incan in order to have the same amount of light reflected back to the user. So absolute brightness should also not be a primary consideration.
Another advantage of staying incan is that it gives you options for filters. Since filters are subtractive, not additive, the desired colors must be in the light to begin with. If you wanted to use night vision gear, for example, an IR filter on your incan light will do the trick very well. A dedicated IR LED would typically be necessary to get similar IR output. Likewise, LEDs don't typically contain much red light compared to other colors, so filtering out everything but red won't leave much output. (LEDs typically produce an overabundance of blue light, so a blue filtered LED would likely be better than a blue filtered incan.)
A well built, potted LED engine will likely be much more durable than an incandescent lamp assembly. I believe your bezel is designed to absorb recoil shock, though, so the recoil won't be as big of a factor to the lifespan of a lamp assembly as much as the relatively short life of incan lamps in general. LED engines are very sensitive to heat, so heat dissipation is typically an issue that has to be addressed. In a weapon light, that is not likely to be an issue, since it probably won't be on for extended periods of time.
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