Manchester City will be the toughest team which Arsenal faced if we compared to other teams on their schedules this because only Manchester City is the team who Arteta cannot be defeated in the last 5 meetings but regarding the match indeed i don't think playing defensively isn't an option for Arteta because Arsenal under him were never been playing with this style even during this season we can see Arsenal almost be dominate for each matches and playing full attacking
The match with Manchester City is a biggest one for Arsenal in rest of season as they are two direct competitors for the Premier League crown. Arteta and Arsenal don't have to win that match, they need to have a draw, prevent Manchester City to reduce 5 points gap and move on to collect points from other teams.
However, Arsenal will have to meet two other big clubs, Chelsea and Liverpool. Between two matches, I see a match with Liverpool is harder for Arsenal because different than Chelsea, Liverpool are still fighting for top four and they don't play against Arsenal without clear task like Chelsea.