It baffles me why people seem to think that playing at Wembley will be a big advantage for United. Why exactly?

The pitch is about the same size as Barca's pitch. A standard international pitch size that every single Barca player will be well used to playing on. It's not as if it's a home game for united where the crowd would be 80 or 90 percent United fans.

Where's the logic?

You would have thought that a United team would be more used to, and suited by playing at Wembley than Manchester City were. Didn't do them a great deal of good did it?

If Barca go a goal up, United will find themselves wishing they were playing somewhere with a smaller pitch so that they could get the ball back.