In terms of the output, throw, and runtime, most of the reputable manufacturers are now adhering to the ANSI FL-1 standard which allows us, the consumers, to measure the products against one another. Also standards for shock resistance and waterproofness (IPX-?) and the type of anodizing (Type I, Type II, etc) allow us to compare the products on those grounds.
The fact of the matter is, it's not the wild west anymore when it comes to comparing lights, at least not among the major manufacturers. In reality, some of the little things like a light's fit and finish, consistency of LED color temperature, user interface, and intangibles like customer service are starting to become the distinguishing factors that render a brand reputable or... notorious.
Fortunately, there are several very dedicated reviewers that spend a lot of time comparing lights on their primary as well as secondary features and posting that information here for us.
In short, it's a great time to be a consumer in the LED flashlight space.