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.
I don't think it will be a very good plan if FC Porto is going to play more of defense in the returning leg again Arsenal at Emirate Stadium, the one goal victory that Porto got is not enough to see them progress to rhe next round this is because Arsenal will come all out with a lot of pressure to see if they can get an early goal then they will push attack but once they find it difficult to score they will fall back ro defend the one goal they have while they keep pushing to ensure they get a winner goal even they it won't be an easy game for them.