A hand-held light is BEST; everything else pales in comparison. I work night shift big-city police patrol, and consider a good hand-held light to be more important than the handgun. I bring three hand-held lights to work with me: Surefire M3 Millenium, Surefire M2 Centurion, and Surefire 8N, the latter being rechargeable.
That being said, a weapon-mounted light is a good thing. I use a Surefire X200, one of the early ones, before they went to an A and B designation. Now that the X300 is out, the X200 may be out of production; my X200 still performs well, so I have not looked at the newer ones much.
I believe there is no such thing as hand-held light VERSUS weapon-mounted light. There are times that one does NOT want the light and gun to be pointing the same direction at the same time.
Night sights are a mixed blessing. Someone will probably post a rolling eyes smiley in response, but I am going to say it again: Night sights can betray your position to an adversary in the darkness, depending on how your weapon is oriented, and his relative position. I am not saying night sights are bad, because I am not; they can be an great, wonderful asset.
I have used, and really liked, the Heinie Straight 8 set-up.
Another set-up I use and like is a factory tritium front sight, paired with the standard non-tritium SIG rear sight, an old classic by now once well-known as the Von Stavenhagen rear sight.
Two glowing dots in the rear sight, meant to give the shooter a three-dot image, is not my cup of tea, generally, though I once had a Wilson Combat pistol with orange rear dots and a brighter, larger green front dot, that worked well.
I live fine without lasers, and have not looked much into that direction. One thing to keep in mind is that a laser will not allow one to hit a target better than any other system, if the shooter jerks the trigger during the pull. Plenty of folks get a good sight picture with regular sights, then jerk the gun during the trigger pull. A lasered target will be missed by such folks just as surely as the target acquired with iron sights.
One consideration with lasers is multiple shooters on the same side not knowing whose dot is whose, if both/all are aiming at the same target. A family or other type of team should keep that in mind. This factor is the main reason cited by my command staff as the reason officers with my PD are not allowed to use lasers on our weapons.
It is also very important to consider the sight-in distance with lasers. Bullets travel in an arc, but light moves in a virtually straight line. Moreover, "close enough" at 5 to 7 yards may not translate to a good point of aim/impact at 100 yards, with windage or elevation. Don't take a long shot, using a laser, if you have not practiced at that distance with the laser.