Hi.
Not sure how much help I can be. But you are correct, CREE LED emitters are the most common in torches/flashlights. Although you can still find others.
Each CREE emitter type or series has a name, usually 3 letters long.
Such as:
XR-E
XP-E
XP-G
XM-L
There are others, but these are the more common.
The XR-E is quite an old emitter now, but very mass market, so you still see a lot of lights using this, especially in the budget world. And in fairness it is still quite a good emitter in its own right.
It’s biggest trump card is it has a very small die area, this gives it a high relative brightness and means it is generally good for throw (long distance). Although total light output is on the lower side.
The next most common is probably the XM-L, this is a newer emitter and is physically much larger than the XR-E. It puts out a lot more light too (lumens), but due to it’s size it has a lower surface brightness, so depending on the application it may offer more flood and less throw than the XR-E.
The vast majority of budget lights found at places like Deal Extreme will be using these emitters.
XP-E and XP-G are less common and sort of git between the XR-E and XM-L in terms of output. The XP-G is more common in premium lights, probably because it fills the niche of jack of all trades, fairly throwy but with plenty of flood and spill.
That said, since the end of last year CREE has been updating it’s emitter range with a new series, so you are likely to see XP-G2 and XM-L2 listed more frequently (and maybe even an XP-E2). They follow a similar trend to the earlier series in terms of relative performance to each other.
To make things more complex, all LED’s are also “binned”. Basically categorized by output. A low bin XM-L will be a lot less bright than a high bin one.
There’s more info here is you want to read up on it: Cree - Flashlight Wiki
But basically if it’s an XM-L you want T6, U2 or U3. If it’s an XR-E Q5 or R2. And XP-G R4 or R5.
When it comes to tint they leds are also classified, although not ever tint is available for every bin or even every emitter.
Tints may be listed as 1A, 3C type of designation. Although often just grouped into CW (cool) NW (neutral) WW (warm). Most budget lights are CW or worse.
There is a growing following of Nichia219 emitters, these offer very high CRI which most of the CREE’s struggle to get close too. But overall output is limited with the Nichia’s and only a handful of lights can be bought with them.
In terms of light brands, best bet is either take a chance or research first. Many budget brands seem to be interchangeable with names, so a claimed name doesn’t really mean much. And the spec of the driver can vary from place to place or even batch to batch.
The Crees seem to have taken over the market, and the Luxeon and SSC products seem to have been replaced.
But, I give them away, and there are still too many in my drawer! 8)