Greens run a lot hotter and eat batteries. As mentioned they are easier to see. Reason they look great on TV when the cops and military use them is the wattage. Civilians are 5 mw max and LEO and MIL can be up to 40 mw. A 40 in red is even visable during the day.
Greens are also traceable. You can follow the beam back to the shooter. Reds are not unless foggy. smoky etc.
This is news to be me, I know IR lasers(usually operate around 45mw) are restricted to LE/MIL, and I'm not quite sure but I don't think there are any weapon sight lasers that go above 5mw for ANYONE, these would insanely bright and relatively unnecessary. The main reason IR Lasers are so much brighter is they are used for marking at extreme distances in coordination with other weapons systems. If you want a little red dot on your target during the day, get a reflex/holo/red-dot sight, lasers in the military are mostly used for marking targets and/or in conjunction with NVG's, or for power point presentations. Lasers in the police and civilian world are used as show of force(I'm not sure why, a gun pointed at me is certainly just as scary as a laser on my chest and if its on my face I can't see it). IMHO Lasers encourage poor target recognition, if you can identify the target enough to line up the sights your shouldn't be pulling the trigger, if you can see your sights chances are he can't see you and then you haven't used proper escalation of force and your lethal force may be unjustified, night sights are the way to go for me. On the flipside, laser sights are good for fast target acquisition on a tactical range or if you are in a firefight. Self Defense situations should be a bit more cautious about using these, not saying they aren't great if your drawing from the small of the back while the perp has a gun on you, but chances are you are going to find yourself using a laser sight while you are lying in your bed in the dark with a burglar not knowing you have a gun, yes its great way to say "hey gtfo, I'm already sighted in on you" but if you NEED a laser to make sure your aiming at him you should probably reconsidering pulling the trigger, because he might not be a person you really want to kill, or he might not know your even there and a blinding weaponlight would establish both far better than just a laser.
Key Points-Lasers are primarily for show of force, or marking targets while using alternate weapon systems. Secondary uses include FTA and low light targeting confirmation. A green laser will be just as effective as red laser for either purposes you are most likely to encounter, and remember positive identification is priority before you pull the trigger, think before you shoot.
IF you are looking at doing day time tactical shoots, I would once again recommend a good quality Holo/Reflex sight. If you really want the best laser sight, a green laser is more visible to the human eye so it will appear brighter, both are limited to 5mw by practicality reason.(EDIT: both are limited to 5mw for visible wavelengths if they are Class3R laser products, 3B laser products are limited 500mw which means they are probably restricted to licensed/certified professionals. The PEQ15 I have is class "3B" laser product, 5mw VIS 650nm laser and 45mw IR 830nm laser, this confirms what I've read that restrictions differ based on visible vs IR lasers) They recently updated the laser classification guides and they don't give finite definitions for wavelength to power output but I would assume a 45mw IR laser is classed the same as a 5mw vis laser by FDA/IEC standards, ITAR regulations limit IR laser products to LE/MIL. Hope this helps