The xp is given out after the op ends and you can earn the accolades with or without your clan.  Which is better just depends on what you want to do and how good your players are.  Since only one person amongst both teams can win the accolade per match, working with your clan may improve your clans odds of having at least one member of the clan getting the accolade.  However, I played last night solo and had no trouble picking up the accolade in roughly half of the matches that I played despite being in the room with other clans trying for the same goal.  Of course, had I played with my clan, the clan may have gotten to 10 total accolades faster. I"m not sure how I'm going to play tonight but lucky for me my clan is already 6 accolades in.  Tis the benefit of having a large international clan.