In my view, the Trijicon HD orange-green sights are best. They are steel & designed for LE duty or hard use.
Many US police & military forces use Trijicon sights.
Wayne Novak,
www.novaksights.com are impressive too. Novak is a top US pistolsmith. He helped co-design the S&W third generation series and the more recent SR1911 .45acp line.
I like the XS Big Dot tritium system too. It's fast to use & bright.
As stated, my 1st choice is the Trijicon HD.
Clyde
www.trijicon.com www.brownells.com www.natchezss.com