I regularly have 1v1, 2v1 and 2v2s at friends houses on Fifa 10.
I can safely say that in a 2v1, the 2 players have the DISadvantage.
no it isnt.
if you have 2 decent players who know how to play doubles, then 2 players is an advantage.
doubles is a different game compared to singles, i could play against one of my cousins all day and the games would be close, we could then do a doubles with me and another cousin vs him and i would wipe the floor with him in every game.
2 decent players against 1 decent player its an advantage.
1 decent player and a crap player against a decent player and its a disadvantage.
it all depends on the skill of the guys your up against and whether or not they can play doubles well together. if your playing doubles the trick is not to pull any defenders forward or out of position, if you do then your basically letting the other team have a 1 on 1 with the keeper due to 1-2's.
its also an advantage because the guy is sitting right next to you and he can either give/receive instructions from the other player. for example
run down the wing
through ball
pass down
pass up
high through ball
also if 1 of them is a corner or free kick specialist they can swap controllers in order for that person to score every time. i have a cousin which cannot miss a free kick from anywhere in the opponents half, even 45 yards out. giving away a free kick to him is like giving away a penalty, 9/10 he scores.
also you can make runs AI players wouldnt normally do, making it far easier to set up or play in that team mate. 2 players is an advantage but only if they are both decent and know how to play doubles well.