Hi skrie!
I would recommend the U2. Firstly, its Surefire, and it uses Luxeon LEDs. This is important for one very good reason. Although SF lamp assemblies are highly reliable, Luxeon LEDs are even more so (IMHO). And in times of crises, the less things to worry about, the better. Also, in my experience, the second brightest level of the U2 puts out as much light as the G2, and at least twice the runtime. Plus it is regulated very well at that level.
A word about reliability. According to Lumileds, almost all Luxeon LEDs that fail, fail within the first few minutes. So in practice, if you put the U2 through one battery change with no problems, then it should last a lifetime (or two...
).
The clickie tailcap of the U2 is another plus. Just grab and push the button and you have constant light.
The U2 also has the added advantage of being a blinding light, so it can double as a defensive weapon. The L2 does not blind as well as the G2 or U2.... (YES, I have tried on myself.......!)
Don't worry about the flood light though, the U2 puts out a very nice corona. And if you really want it to flood the room, just point it upwards toward the ceiling and the reflection should be sufficient. The L2, like Size15s said in another post, can be considered a low level light with a high-level option.
As for me, there's a reason why the SF U2 is named the Ultra!
But to be fair, here are several advantages of the L2 over the U2:
1. L2 is cheaper
2. Two levels of light are really quite sufficient
3. It is easier to manipulate the L2 to get the level of light you want (simple one handed operation) compared to the U2 when you sometimes have to use both hands (but one handed operation is possible).
4. When the U2 drops out of regulation due to weak batteries, you can only get the lowest level of light (about 5 lumens I think) and you have to manipulate the selector ring to the lowest level and turn it off and on again. With the L2, with weakening batteries, you get the first level, at least 15 lumens for about 15 to 30 minutes, so you are assured of at least 15 lumens of light anytime you grab the L2 (provided you don't deplete the batteries completely).
5. It is easier to carry the L2 in the pocket. So if you get the U2, you'd want to consider some holsters or a lanyard.
6. The "Wall of Light" from the L2 is true.
As always, try it out before you get it. With Luxeons, you need to be slightly concerned about the tint, so try different models and see which one you like.