I think you really need to consider two lights.
If your brother flies into places like Goroka, Port Moresby, or the Outback where there are absolutely no CR123s readily available, a AA-powered light should handle duties for preflight checks, including being able to shine a decent amount of useful light three stories up to the tip of the 737 tail. There are plenty of good lights out there in the 3-watt range; check out all the advice in this thread alone, but at the very least the light should have adequate heat sinking so that the LED not get too hot and become dim with continual use.
I have several 1-watt and 3-watt LED torches and have found that most LEDs (even the good "throwers") will not provide the same amount of light as an incandescent torch, but that is another story. Our aircraft are mostly single-engine Cessna types where even a 1-watt light is adequate for a pre-dawn preflight, but the incans really shine (pun intended) when peering inside the cowling during the day.
In addition to a preflight torch I believe you should consider a keychain light for reading checklists and charts. While both CASA and Boeing designed cockpit lighting into their equipment, in the real world lamps do burn out and electrical systems go mad at the worst possible time. A keychain light such as a Photon, Inova, or those sold by County Comm are very handy tools. These lights come with single 5mm LEDs which are great for providing enough light to see inside the cockpit without losing night vision, and the LEDs draw little power allowing the tiny batteries to last a long time. One of our pilots lost the interior lights one night and was able to safely complete the flight by holding a Photon microlight in his teeth in order to see the instrument panel. Another of our pilots always clips a Photon to the headliner (and turns it on for the entire duration of the flight) as a backup when flying at night.
Less than 2 weeks ago I bought 10 of the County Comm SO-LED clip-on lights and 4 each of the red and blue Simple Pocket Lights. I haven't dunked them in water, I haven't thrown them against the wall, I haven't given them to a 5-year old or stepped on them, but the one I carry on a keychain in my pocket has worked great for lighting the walkway to my garden shed or for lighting the lock on my car door so I can find the key slot. The SO-LED are only available in white at this time, but the clip is easily transferable to any other color of Pocket Light. The price is reeeeaaaalllly hard to beat at $1 USD per Pocket Light and $1.50 USD per SO-LED.