Meh, I don't play FPS at a competitive level, and I have no intention to. I play to have fun, and as long as my minimum sustained FPS stays above ~20-25 the game feels smooth enough to me. Heck, on my old system I finished HL2 when almost any use of the gravity gun would drop my FPS so single digits, and I still enjoyed myself.
If I'm getting pretty much the same framerate on my system at 1920 as I can at 1280, then I'm going with the higher resolution. I don't like jaggies, and at higher resolutions I can spot things farther away in-game. It's easier for me to distinguish between a smoker and a common infected when they're made up of twice as many pixels to give detail.
That said, most LCD monitors are limited to 60hz, even if they can accept 75hz input (The exceptions being new 120Hz LCDs meant for use with 3D goggles). That, and the human eye is decidedly not limited to 75hz, I don't even consider myself to have fast eyes and on a CRT 75hz looks flickery and gives me a headache.