FPS Multiplayer - What do you prefer more, realistic or extended lifebar?

Hey,

So what do you prefer? Quick death like in Counterstrike where even a fart could kill you or a longer extended lifebar (due to shields etc) like in Halo?

I myself am leaning more the Halo-route, altho I think a headshot should always be instant kill.

I say somewhere inbetween. I think call of duty is perfect. I believe snipershots should instant kill, as well as headshots. and it should take quite a few bullets to kill someone, but no where near a full clip.