Years ago, I was mildly against lights/lasers on handguns. For one, the technology was not nearly as good as it is now, and I didn't find them of much or any use. Now, the good ones (Streamlight for me, currently) are solid, reliable, and work very well. Most are still a little bulky for EDC, but for HD, I consider the light essential, and strongly in favor of a laser.
After much thought, and owning both, I prefer red laser, here's why: red is more shock resistant/reliable, easier to find outdoors in foliage, uses much less power (batteries last longer), oh, and its cheaper . Green is easier for the eye to pickup, and it seems much brighter, can create more of an ambient light effect. Really, both are excellent on a HD gun.
Those are actually made by Blackhawk and have the Serpa attachment pattern on the back. So any attachment devices that work on a Serpa will also work on them.
Thread bump - recommendations for a rail-mounted light/laser combo for a S&W MP40? This would be for a nightstand gun, and given that the pistol is a standard full size model, light size and holster fit aren't big concerns. Not sure what my budget is, but I'm going to plan on needing to spend a couple hunnert to get solid quality, unless Dvor or somebody comes up with a great sale on just the right light.