Xing,

I have the Inova X5 (the HA-III, sterile, subdued version), and there's no comparison to the L4. The 5 5mm LEDs in the X5 don't put out anywhere near the light of the L4. Shone on the wall, where the beams overlap, the light from the X5 is barely visible. It's about comparable to my modified L4 on "low", maybe a little less bright, though it's hard to compare since the tints are much different.

The X5 is, however, reportedly very efficient at sucking the last bit of life out of CR123 cells, and several people report getting hours and hours of further use in the X5 out of cells that are no longer useful in the more powerful lights. That can be valuable, especially if the "primary" light is for critical use, and you change cells frequently so as not to be caught near "empty".

The specs on the Streamlight look similar, but you'll find that they feel much different. Next to the surefire "E" series, the Streamlight feels bulky, heavy, and a bit clunky... and too large (especially the head) for convenient pocket carry. The quality of the Streamights is very good as flashlights go, it's just not in the same league with Surefire.

A lot of what you're paying for on the Surefire is details. The anodizing is HA (hard anodizing) III (type 3), which is many times harder than earlier version- apparently SF has demonstrated this by using the (knurled) SF body to actually saw through a "normal" aluminum flashlight. The SF has a pyrex lens, which is both heat resistant (all these tiny, powerful lights can get pretty hot) sturdy, and scratch resistant. The LED is the Luxeon 5, brighter and more even than the Luxeon 3 series. The reflector is better engineered- you'll be amazed how even the light beam is from the LED lights. Machining is very tight and precise througout. The "clicky" switch is very positive and intuitive.

By contrast, both the Streamlight and Nuwai QIII are Type 2 anodized (like, say, a mag-lite) which wears much faster. The LEDS are Luxeon 3s, and almost always have a marked blue or violet tint. The regulators will be much simpler, probably voltage-only. The switches on both operate a little differently than SF- when you push it DOWN, nothing happens.. when you let it back UP, the light comes on. No big deal unless you need a "momentary" flash, or to flash Morse code or something, then it might be a problem. And on and on...

All of these are fine flashlights, none are perfect. Whether some or any of them are worth the cost is not something I can determine for someone else. The Streamlight, for example, costs less than half of the typical street price of an L4, and probably povides 80 percent of the functionality... and for 95 percent of the users, that 20 percent won't make any difference at all.

One disadvantage of the L4 is that the beam doesn't carry as far as incandescents, and not as far as most Luxeon 3 lights.. it's more of a "flood" as opposed to a "spot". I'm in city and suburbs a lot more than out in the country, so that's to my advantage, but some dismiss it on those grounds.

Please do check out the excellent series of photos in the thread that Burncycle pointed out here:

German Flashlight Thread Photos

The text is in German, which doesn't help me much (it's not much better piped through Babelfish, either), but the light used is in the lower left of each photo in red.