Here's a "big picture" answer that you are unlikely to get searching these forums.
See the recommended threads for explanation of each company's bin structure.
Here is a valuable page from The Sandwich Shoppe that explains Luxeon bins.
When a company (let's say Lumileds, maker of the Luxeon line of LEDs) makes a white LED, they have target values for luminous flux (how bright it is), color (what shade of white), and forward voltage ("Vf" -how many volts of DC it takes to produce light). If they could make all their LEDs at their target values, they would. However, the manufacturing process and materials for these LEDs have minute variations that make each LED brighter, or dimmer, higher or lower Vf, or yellower, or purpler.
They choose a target value near the center of the statistical distribution curve for these values so that most of their products fall within the advertised specifications. Some LEDs will be dimmer than spec, some will be brighter than spec. Ditto for Vf. They test the emitters to determine how bright, what color, and what Vf they are. Then they sort them into "bins" according to the results. We usually refer to a Luxeon LED as a "U-bin", or a "W-bin". This refers to the flux, or brightness bin.
Exceptional LEDs, with high flux and low Vf are called "flyers" by Lumileds. S-bin Luxeon 1, U-bin Luxeon III, and X-bin Luxeon V emitters are flyers. They are relatively uncommon, and exceed most of their customers needs. When they fill their typical customers' orders, they don't include flyers. You wouldn't want to make a traffic light, or an electronic billboard with a couple extra-bright LEDs. That would be a flaw. The more control Lumileds has over their materials and processes, the fewer of these exceptional LEDs they will make.
Lumileds does something stupid with their distribution system. We call it the "Luxeon Lottery". For small orders, you can only get Luxeon LEDs from Lumileds' partner distributor, Future Electronics, Inc. You can only specify that you want a white Luxeon III for instance. You can't select individual brightness, color (tint), or Vf. When you get your white Luxeon III, it may be awesome, or it may be crap. You have no control. If you order a large quantity, you can specify certain bins, provided Lumileds has them on hand. However, Lumileds charges a premium price for them.
Flyers are what we look for to use in flashlights, because we want the brightest LED with the lowest Vf. That is one measure of efficiency. Some companies like Cree, seem to be more cooperative with bin selection, and may have smaller minimum order quantities.
You should realize that flashlights are only a minute sector of the LED market, so the manufacturers don't really care much about our desires or complaints. an order from a large flashlight manufacturer may be a few thousand emitters. An order from a billboard company may be several hundred thousand.
The manufacturer of your flashlight may have been able to specify their bins, so they might advertise the bins of their flashlights. Some companies may have several to choose from. Usually just two or three. They will charge a premium for their brightest lights. Some flashlights discussed on this forum have flyer bins available. For Luxeon III emitters, T-bin is common, U-bin is exceptional.
Bernie
