You're going from a $50 light to a $300 one, there's a lot inbetween.
I learned quickly to skip the cheaply made, heavily hyped imported lights. They work fine, while they work, but then they don't work, usually when you are in the dark and in need of a light. Surefire lights really are worth the money. They're the Sebenzas of flashlights (like another poster said, the benchmark for the industry). The expensive price is justified by the quality of the product, and the incredible warranty.
Imported lights advertised lumens are most often way off. Surefire lumens are conservatively low. I've seen "850 lumen" Chinese lights that weren't nearly as bright as my "500 lumen" Surefire P2X. I'm not sure what exactly the lights were putting out, but the Surefire was brighter.
The more complicated you get, the more likely your light is to break. Adjustment rings, 3 or more modes, etc. all make the light more likely to fail when needed. If you want reliability, find a light with 2 useful modes and stick with it. If you have to go cheap/inexpensive, go simple. Streamlight makes their Microstream lights that are very tiny (single AAA) and quite bright with a very long life using lithium batteries. They are extremely thin lights that also have a pocket clip and carry easily. The Microstream also has a single clicky button so there is little to break or go wrong. Oh yeah, as far as batteries, if you get an AA or AAA light don't put cheap alkaline batteries in it, they often leak/explode/ruin lights.
I highly recommend Surefire's E1B. It's a smaller pocket sized light that runs on a single CR123A battery. It has two modes, a very bright 200 lumen high mode and a just bright enough 5 lumen low mode. I use low mode 99% of the time, and the battery lasts for something like 35 hours but I change it out every few weeks anyways. The "Tactical" version has a push button pressure switch (doesn't "click" on) that I prefer because you can also twist it on or off in addition to the pressure switch. The most breakable part of a quality flashlight is the push button, and if the pressure switch ceases functioning you can still use the light by twisting it on or off. It also allows you to instantly switch between low and high mode, because if you push lightly it activates low mode, push harder for high mode. I believe that the Click version turns on the high mode first, which sucks when you don't need a blinding blast of light because you want to preserve your night vision. They can be found for $140ish, I've found mine to be worth every penny.
After owning, and using, dozens of lights from Klarus, Nitecore, Surefire, Streamlight, etc. the only ones I trust are the simple Streamlights and the high quality Surefires. I've been left in the dark in a dangerous situation before, there's little reason to risk it using substandard lights.
