I have experience with the Surefire X200, the Streamlight TLR-1 and TLR-3
X200: very high quality, not quite as bright as the latest Streamlight offering (the X200 is an older light). I like the fact that if you push the rocker in any direction it locks on, and if you push it foreward it is like pressing the tailcap on a conventional light (instant on, instant off). My only gripe is the price and the fact that the mount seems a little tight on the M&P frame. I imagine that the current generation Surefire lights are brighter and may mount slightly better on the M&P (it looks like the switch just presses hard against the trigger guard- it does not affect function, but it can be a bugger to get on and off).
TLR-1: very good light for the money. Much cheaper than the Surefires, and brighter than my X200. A lot of my guys at work have them on their guns, and I have yet to see one fail. My only complaint is that the rocker switch is constant-on one way, and instant-on the other. If that works for you, great...but if you want it the opposite way, I'm not sure you can reverse it.
TLR-3: small and bright. It is much smaller than the TLR-1, and still bright enough for serious use. I like it because it doesn't stick out beyond the barrel and is narrow, so concealing it is a LOT easier than concealing a TLR-1 or any of the Surefires. The rocker switch works the same way as the TLR-1.