USAR, IMO, means C cells. I've been through floods, tornados and hurricanes, and C cells always seem to stick around. When I get called out on that kind of stuff, I tend to stick with something waterproof. I was using my dad's Pelican Super Sabrelite until I realized I was down to my last bulb and that the design is so old that I can't get bulbs anymore, so now I use a Kohler Bright Star 3C Responder, with an Epieon LED module. Sure, it cuts the HL rating out, but it's still better than the cheepie lights that are issued to us. Once the "disaster" is over, I'm more than happy to use my good lights; The A2 is my go-to light for administrative purposes, and it most recently served a tour with me in the wilds of Alabama during the hurricane season.
Most of the guys on my team are using LED headlamps of some sort. About half are still carting around the issued light, a cheepie 2D light of less than dollar bin quality. The other half are using Maglites of some sort. I'm the team flashaholic by far, with my assistant in second with his SF collection and our safety guy in 3rd with some cool LEDs he has accumulated through his career in the military, as an LEO and SWAT Team member.
The one thing I try to do is keep a couple lights that use every different kind of battery there is, so in the event that I could only use battery X I wouldn't be out of luck with no light that uses said battery.
GreenLED, I'd go out at night any time that I'm needed. Especially with a lost person, you're going to start at the point they were most recently seen. The longer it takes to start searching, the farther away the person could potentially be. A healthy person in decent weather who is just lost wouldn't be as critical as someone who is injured, or an elderly person who hasn't had their medications. It's all relative, really.