Which better Assasin or Combat for 1 vs 1 pve?

Im Assasin player, but i need to know which better talent for pve

Assassin for selfish dps, combat for %4 damage buff (pychical) with nice dps. While there always be assassin buff, there wont be any %4 damage bonus since only alternative is arms warrior.

Are you talking about 1v1 in PvE gear or which spec does more DPS in PvE? I'm going to assume it's the latter.

Which realm are you talking about - Lordaeron or Icecrown? Generally, Assassination is better on lower gear and Combat beats it at high gear, being one of the top DPSers on WotLK. So if you're talking about Lordaeron, then Assa is the right pick. For Icecrown - if you're over 5-5.5k GS, then Combat will be better.