There was a short period of time when SureFire bought bulbs from Streamlight. Streamlight was nearly bankrupt from losing a huge lawsuit for patent infringement. SureFire needed a bunch of bulbs and quickly. So Dr John Matthews injected some much needed cash into the veins of Streamlight. Soon after, ironically the Streamlight Scorpion was in direct competion with the SureFire 6P for a huge US military contract. But once both gained a foot hold in the world of hand held flashlights both agreed to no longer compete for the same contracts.
Streamlight has quietly gone about the business of supplying law officers, fire personnel, rescue folks and many blue collar workers a good product at a decent price. SureFire went after the market where people dodge bullets or kick in doors for a living. Their target market was folks with an even more extreme line of work than cops and firemen.
In the 2nd hand market Streamlight has always taken a back seat to SureFire concerning resale value. But to a flashaholic that means a great product can be had on a budget.