I say it depends on what type of game I am playing. but for the most part if it involves a gun or some type of aiming I go with 800x600 because it makes things huge and easy to hit.
I make up for the low field of view by cranking up the mouse, so with the big heads you dont need to be sniper steady with the aim. and besides I am much more of a up in your face with the sawn off type of player. That or a sniper, one of the two extreems, but preferably up close UT flack cannon style. Not a good mid range fighter and thats why im not so good because most fighting is mid range.
one other thing about being an up close fighter, it is so much fun to just run in the base balls out with the shotty kill 75% of the other team then once your dead have the rest of the team come in nab the flag and I will be respawnd at my base grab a sniper and cover the team running back.