How is an MJLED different from any other high output LED?

Sorry for the ignorant question, but what is the difference between putting a MJLED in my minimag VS. putting one of KevinL's 35K mcd white loose LEDs (seen here)? Is the MJLED just optimized for the minimag? Is there something huge and simple that I'm missing (this seems like a strong option)? Please fill me in! Thanks,
Abe

From what I understand the MJLED are supposed to have a low Vf that works well with 2 AA batteries.

I don't know all of the technical details, but the MJLED's have a much larger DIE, much better thermal capacity, and can work at a continious 100mA or so. They are MUCH brighter than the 35K LED's, and it is a perfect upgrade for a standard 2xAA MiniM*g

For best optical performance, MJLED's are ground down (also called cut-down) to make them work better with the MiniM*g reflector. So sometimes you will see both, the un-cut and the cut-down version offered for sale, but for a M*g mod, I would definitely recommend the cut-down ones. The Sandwitch Shoppe had them at some point - I don't know if they still sell them or not.

Will

As far as anyone knows, the MJLED is an ISP 100-mA LED, hand-picked for low Vf, and cut down. Most LEDs, including the 35,000 mcd LEDs, are spec'd at 20 or 30 mA. If you run them much higher, the life is severly reduced. The ISP LED will handle 70 or 80 mA just fine. The low Vf means the LED works better with a pair of alkaline or Energizer lithium AA cells. Cutting the top of the dome off means that light is emitted more uniformly, allowing the Minimag's reflector to focus the light forward. If you put an uncut LED in a Minimag, the LED emits most of the light forward (focused by its own dome), emitting very little light to the sides for the Minimag reflector to catch. The Minimag reflector is pretty small to start with, so I don't know how much of a benefit you get from cutting down the LED.

Yeah, as far as a comparison, the cutdown MJLEDs on two Lithiums or even on two alkalines, is puts out more total light, a wider spillbeam and a tighter hotspot (so more throw) than the 35k LEDs do, even when the 35ks are on 3 alkaline cells. The MJLEDs look a bit blue when not compared to anything else, but only slightly. The 35k LEDs look slightly violet compared to my MJLEDs.

Of course, the runtime on the MJLEDs isn't as good as the 35ks.

1) The standard ISP LED has a 25 degree view angle, throwing most of its light forward. Very little light gets to the reflector giving a very weak hotspot. MJ (Micheal Jorden) cut off the front of the LED and polishid a gentle curve. This throws much more light to the sides at the reflector creating a much brighter hotspot.

2) The MJLED is a 100mA LED. It is much brighter than the typical 20mA LED.

3) The MJLED 2nd generation or later has a low Vf measured by other CPFers at 3.04V allowing the use of 2 alkaline batteries without a boost circuit. Other white LEDs have a Vf of ~3.6V requiring a boost circuit, lithium batteries or 3 alkaline batteries.

Because the minimag uses a bi-pin bulb, the wires of the LED will slide into the socket making a direct LED to bulb replacement possible. Hence the popularity of the MJLED/minimag upgrade.
Cannot do that with a PR bulb flashlight until Terralux came out with the BA-1 & BA-2 PR base to bi-pin adapter. I have sucessfully converted an Energizer stretch flashlight/larea light with reverse polarity wiring with the BA-1/MJLED combo.