Well my emergency survival pack, for surviving a minimum of 10 days in the wilderness is equipped only with a Petzl tak-tikka plus headlamp... multiple levels, 3 AAA batteries, red and white light... runs for several days solid before needing batteries, and I carry about 2-3 changes in my pack.
On me at all times are an additional 2-4lights, plus a couple photon freedom microlights.
I would highly recommend a headlamp since in a no power situation it's the easiest to work with hands free... RUNTIME is the priority, and easy access to batteries... the thing I don't like about the petzl is AAA batteries, I would prefer AA's so all my gear was on the same system... I have a test unit we bought from Photon, the Photon Fusion headlamp, and so far am liking it above the petzl, it is larger, however is regulated, has red and white led's, and uses AA batteries. Multiple levels of light, including flashing.
I would highly recommend at least 1 or 2 lights beyond the headlamp, a c/d sized light such as a propolymer 3C (multi led model, not luxeon) or twintask 3C something with a large runtime, and readily available batteries...
Avoid odd cells such as 123's and rechargables. A primary rechargable to allow the light to be used daily is ok, as long as it takes non rechargeable, and they are kept near by.
It's one thing to have 20+ 123's on hand, and think you have enough, but after a week, if your running out, what battery do you think your likely to find at a store or such... AA's they are the most common battery IMHO. I personally would choose a 3C/D light as they run for a while, and cells are cheap... get a big pile of them... then back it up with a couple AA lights, such as a fenix L1P and perhaps a pro-polymer AA or something...
Again runtime is more important than brightness, multiple levels are always a bonus as you have light in reserve. Blinding light is good for more defensive nature, so perhaps one that CAN go fairly bright, perhaps a G2 in reserve for a defensive light, since they are fairly low cost.
I don't think there really is a best light, however there are features in the best lights.
LED - last longer, don't break when dropped, longer runtime
Common battery sizes, C, D, AAA, AA (Best IMO is AA)
RUNTIME - when there are no lights at all, even 5 lumen's is a LOT!, so go for something that will run for days before a battery change, if at all possible.