I've used both Meprolight and Trijicon night sights on pistols. Both are well made (of steel). Neither makes sights for everything, but between the two, you can outfit almost any pistol or revolver.
Meprolight Sights are brighter and appear larger in the dark. They also have a wider white border, which makes them easier to use in good light against dark backgrounds. The tritium cells seem to have a dark center, to my eyes anyway.
Trijicon cells are very small, almost pinpricks, but bright. The area around the cells is smaller, which some people find less distracting.
Trijicon HD sights are well worth consideration for a defensive handgun. The front cell has a large, phosphoresent surround, green, yellow or orange, which enhances quick visual acquisition. It continues to glow for up to 10 minutes after exposure to bright light, intended for enhanced "entry operation" performance. The rear blade has tritum cells without any "distracting" surrounds, and a large, U-shaped notch.