Its gonna be a hard game for both team, but lets take the fan goggles of and lets pretend that we are not united fans for some seconds.
Barca is up to date the best team, probably ever, in the world.
They have a team concisting of really strong players wich are fully capable of keeping the ball posetion 75-25 on every team in the world.
United can't do this, but they have a very strong team aswell and are very good on counter attacking if needed.
Barca has several individual players that can make the day look brighter in a second.With this i mean messi passing through 5 guys and finnish it or xavi and iniestas assist wich can pretty much come out of nowhere.
United are always depending on the team to perform. ofc they have rooney, giggs and hernandez, but in the end its always a team working goal.
Barca has a better team allround than united.
United may have better players in some positions.
I think the most gonna be happening through the center midfield wich united weakest link. Barca gonna tear who ever plays that position.
United key to this game in my opinion is counter atticking game with trying to use nani or valencia to challange on the side.
I think for united to attack will be stupid seing they will loose the center midfield, barca is to strong there.
United best chance in my opinion is to play 4-5-1, that is beacuse they will have enough power in the midle to stop the creative way of xavi,iniesta and messi lurking alitle bit down to start something. They stop them, pass the ball directly to the sides and attack.
This is just my opinion.
My guess barca will win 2-0