Think they're basically around the same as us for the year. Will be a fight for 4th between us 2, dont see anyone else being too seriously involved for 4th.
Their strengths very clearly lie in their front 3, while being pretty shambolic defensively as you'd expect. In midfield think they're a bit overrated and will just be inconsistent. Our strength is a bit more evenly spread out, but we are generally good going forward (but have young players so end product will be inconsistent), have Pogba world class in the middle but inconsistency around him, and then a good back defence/goalkeeper group. I see more room for natural growth with us over the season, while they just need new players in defence (Tierney though might be a big plus).
Last season there was basically nothing between United and Arsenal in almost all statistical measures. Very similar in a lot of ways. United over the summer addressed their 2 biggest issues, but still have some others. Arsenal strengthened their strongest area, while kind of ignoring their issues (don't count David Luiz as addressing that defence, hes shit).