Depends what you want and what team, for barcelona alba would be fantastic as he is quick and is very attacking, while they dont really need someone who is that defensive at the back he can sometimes get back and do a job but with barcelona have 60-70+% possession each game they love attacking fullbacks. If he was to come to manchester united he wouldnt really fit with our style of play, he gets forward and contributes but we dont keep the ball aswell and we would get slaughtered down the left. in my opinion if we were to have him in our team. I think alaba is more our type of player and is very versatile but like you said, why would he want to leave bayern.
Paul Scholes our midfield maestro!