What makes a flashlight brighter than another?

This isn't just to answer my own questions, but rather to enlighten us all, novice to expert. I think most of us here have a decent understanding of how a flashlight is powered and gives off light, but some are obviously better than others at doing this, even when they appear to be similarly made. Two flashlights each might contain an XM-L emitter and be driven the same, but one clearly puts out more light than the other. So what are the core components in a flashlight/torch that set it apart from its brethren? Even when specs appear to be the same, why will one outperform another? Some examples would be: Emitter, driver, reflector, battery, and heatsinking.

What got me wondering about this started when I was comparing the budget knock-off or re-brand stuff to the major brands. So what do you think?

What makes a flashlight brighter than another?

There are a couple items:

1. The reflector, how much it concentrates the light. A tight beam will look brighter and throw longer.
2. The power put into the led, this is controlled by the driver circuit and how much the batteries can deliver. Some drivers can transfer more than 95% percent of the power from battery to led, other only 60%.
3. Not all XM-L led are equal brights, this is called binning.
4. Not all glasses and reflectors are the same, some looses a lot of light other don't. With glass it depends on the type of glass and coating.

The budget knock-off specs are usually wildly overinflated; 700 DealExtreme lumens is probably not more than 300 ANSI lumens.

Some of it is also in your method of comparing lights as far as brightness is concerned. If you point two lights outside at your car 20 feet away the better throwing light will have the advantage but if you point it at the ceiling sometimes the floodier light will make the room brighter because the hot spot of the thrower could saturate your vision and make things look dimmer when you are not looking at it any more. As StarHalo said.... specs are meaningless without a standard and proof in testing. This is why there are people constantly reviewing lights because the specs on most lights are just plain inflated.
Basically there are too many factors in lights to just take components and compare to figure which is brighter or not. Even different brands and types of batteries can make a difference as some can hold power levels higher than others if the light isn't completely regulated that can affect the output. If a light isn't regulated then even the charge of a battery (its current voltage/capacity) can affect the output.

I definitely agree you can't just go by stated specs and I certainly never believe the overstated numbers from the chinese websites. It seems like a good driver can make a big difference and I would think the emitters are more closely shared among high end and budget lights. And then, of course, you can put a driver in there that's really sucking current but then you need adequate heatsinking and that's another cost upgrade in design AND production. It seems like you guys really nailed the core factors that separate the best from the 'best on paper.'

Few things off the top iof my head...

-Flux BIN of the particular LED
-Forward Voltage of the particular LED
-Thermal cooling capabilities of the design / host
-Optical design and quality of optical materials
-Electrical resistance of the host body design
-Electrical resistance of switch