My point is that making a decision about functionality that could make the difference between life or death based on a factor that, when it counts, won't matter at all doesn't seem like the way to go.
I'm running a P30L w/Surefire X400 (light/laser combo) and I totally get what DParker is saying. For a full-size handgun, I doubt the added weight of a weaponlight will be noticeable by most in a SHTF situation and the advantage of not having to fumble around at night looking for your handgun AND a separate flashlight immediately upon waking up is a huge plus.
FYI, the reason why I opted to spend a couple hundred dollars more for the Surefire vs. a Streamlight TLR-series weaponlight is because I didn't like the fact that the TLR-series requires you to weak-hand thumb up (or trigger-finger thumb down) to enable "permanent on"---both disadvantages compared to a weak-hand thumb down motion. For the TLR-series, weak-hand thumb down activates "momentary on" which immediately deactivates once you remove pressure---something you are almost guaranteed to do while firing which can create a strobe effect AGAINST you for rapid follow-up shots. It's nice that Streamlight now offers a dedicated strobe feature (which Surefire does not, last I checked) but that's not enough to make up for its inferior control setup, IMO.
The one minor drawback for the Surefire (which I'm not sure if the Streamlight does or doesn't share) is that you need to dismount the X400 series from the handgun to swap out batteries (requiring you to verify and possibly re-zero the laser).
Going out at night, though, I love my EagleTac T20C2 (that Shipwreck recommended). I am considering getting a smaller flashlight for lighter wear, though.