I am looking for a good tactical light for my AR. The AR has SIR-M installed. I wanted to add a flash light on its right rail. Which (surefire or streamlight) is better? which model? where to get it with a good price?

thanks.

As long as you've gone the extra mile with the SIR, I wouldn't go cheap now.  Although I really like the Insight M3 because it fits on my Glock and on my AR (with mount), your rig deserves a super go-go low-drag light like the SureFire weapon lights.  I'd suggest the SF-M951SU (6 volt, knob mount, tape switch) or the SF-M961SU (9-volt, knob mount, tape switch).  I prefer lighter units because they don't need to light up the whole neighborhood.  Both of these are designed for weapons mounting, and you don't need a vertical foregrip to use them (like the m900).

Streamlight is an ok light, but it is not a Surefire. I use and recommend Surefire's. The small 2 cell lights are good for CQB and will light up a room very well. However, if you move up to a 3 cell light, you've just expanded the versatility of the light (and therefore the weapon!).

The Surefire systems are incredibly modular. Especially the M96 series suggested above. You can get them with ARMS throw lever, or knob attachments. You can get them with a click on/off button, a momentary on/off button, or a pressure pad on/off system. The 3 cell M96 series will work with your standard bezel, or the turbo heads which tightly focus the beam for effective light at longer ranges.

In addition, the center body is the same for all the M9XX series. Once you get that, a mount, and whatever on/off switch you want, you can change from a 2 cell light to a 3 cell light (or the other way around), all using the same center housing, mount and activation switches. All the parts work together and you can have a light for about anything you can think of.

In addition to these advantages, I cant go without saying the beam on any Surefire light will be whiter, brighter, and more pure than that of any other comparable powered light you could possibly consider. Surefire's will be built tougher, and more user friendly. It will be more expensive, but there's a lot more going into these light than just the light they produce. Good luck!

Here, check this link out and see how it all works...

www.surefire.com/misc/MUTLS.swf