Most likely Porto will use a defensive strategy and target a draw at the Emirates, Arsenal will have difficulty beating Porto even though the goal margin is only 1-0. On paper Arsenal chances were very good, but when they dominated the match and created chances, no one could convert them into goals. Porto would really benefit if Arsenal still played with the same style, they also wanted to qualify for the quarter finals and Arsenal failed to anticipate their style of play.
Full defensive is very good tactical for FC Porto on second leg match against Arsenal, get capital winning over one goal and draw result on second leg match more enough for FC Porto qualifying to quarter final although Arsenal's advantage with playing in their home. I think will make frustrated with the opponent team when FC Porto make full defensive strategies on second leg match.
I think FC Porto can take advantage with counter attack with Arsenal will play more offensive make space with their defense position, be careful for Mikel Arteta if Porto will play more defensive and Arsenal payer get frustrated how difficult scoring goals make their defense players will leave their position.
You should make sure you do whatever works for you, and Portuguese side did whatever they could have done to be winners of that first leg.
There'll be so much highlights on the second half at home against Arsenal, the Londoners would have a good chance to win or lose at home.
Gunner's might be doing well in the English Premier League Competition but whenever it comes to the Champions League they ave to double whatever they're going to make sure they go through this round.
I remember the days with Bayern Munich you know, lol, they'd try all they can but Bayern Munich would subdue them.