My advice comes from the perspective of a caver and field biologist.
Decide which type of battery you plan to use before selecting your flashlights.
For me, I greatly prefer lights which can use the most universally available battery available, the good ol' AA. In a perfect world where money was no object and I had a bottomless barrel of lithium CR123 batteries, I'd choose the CR123. It is certainly the superior battery with its high power, light weight, and extreme shelf life.
However, I work in a world where I need to use a LOT of batteries in many different pieces of electronic equipment (flashlights, cameras, GPS, radios, and scientific instruments) and have done my very best to standardize most of my field gear to use high quality rechargeable AA batteries. If one piece of equipment has dead batteries, I can always scavenge batteries from another device I am not using at the time. If for some reason I run out of batteries, I can purchase them from nearly ANY store in any part of the world.
As an extreme example, I was caving deep in the jungle on a remote island off of Panama last summer when I discovered that my headlamp had been accidentally turned on in my pack and I was not going to be able to safely enter the cave with only my backup light. The nearest store was 4 hours away by trail and boat. I was able to buy 4 new generic Chinese alkaline AA batteries from a half naked boy in a native Kuna indian village. Had I needed CR123's, I would have been out of luck and would have wasted an entire day in the field.
Do I own flashlights that take CR123's? I most certainly do. But these flashlights are kept as my emergency gear and are not used for every day purposes if one of my AA powered flashlights will do. I could easily spend $20-30 on CR123 batteries on a single day caving if I didn't have lights that used rechargeable AA's.
So all that being said, I'd suggest that someone new wanting a high powered LED flashlight buy a Fenix L2D and a set of Sanyo Eneloop AA batteries with charger to power it. This flashlight has lots of modes to play with, is well made, and is shockingly bright.