I believe Arsenal will win easily since there's no big threat from Manchester United, their striker are still not that strong. Casemiro and Eriksen need to work harder to make Arsenal's striker not get closer to their goal post.
I don't think Arsenal will win against Manchester United even though Manchester United team is still struggling to get back to good form this season. Arsenal apper to be in a better form no doubt and they will have the advantage of playing in front of their fans which will give them an edge over United but even when they were hot last season with their winning streak they find it difficult to defeat Manchester united team that was struggling. I see the game ending in a 1:1 or 2:2 draw but I don't think Arteta has what it takes to defeat the Erik ten hag's men even though they have not been showing consistency in their performance after three Premier league matches.