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.
A 1-goal aggregate is enough to secure their position and indeed defending the same as in the first leg is a strategy that is still very good for them to do but it will certainly be very difficult for them.
In the first leg we saw Arsenal's dominance was very good, it's just that they missed in the last minute of extra time which made them have to chase the aggregate that happened now but we know for the second leg they will play at their own home which sometimes emirates stadium is very haunted and it could be that Porto must be willing to lose a place.
I think it will be interesting because after all, Arsenal certainly don't want them to be eliminated when the opportunity they have been waiting for for several years waiting to play in the Champions League stops at this time.