I think the whole 2-1 loss over 0-0 is being looked at the viewer's own comfort level when watching the second leg ... because whatever the score-line from first leg, if we have one or two away goals in the bag already, then if (or more like 'when') they score at the Etihad, then we won't be panicking so much having our own away goals in the bank to counter that. It really is only if both ties end up in a draw (on aggregate) then the away goals come in to play. Agree that best is to win outright but I guess the poster arguing for away goals is more thinking of how that can make the second leg slightly comfortable watch to begin with ... not having that and they score first would mean any kind of (aggregate) draw is out of question and that might put more pressure having to go forward and open up more and them being a perfect counter attacking side that can do downhill quickly from there.
Oh well, all these team selections and goal scenarios and first leg this or second leg that are just hypotheticals, it will be what it will ... sit back and enjoy ... we've picked one trophy already ... Premier League is coming shortly ... and we're in the Semi Final of the CL ... no pressure, it's not like we're going for a Quad anymore, had we been in the FA Cup final as well I think we'd be putting a lot more pressure on ourselves.