I also expect Arsenal to win tonight. Arsenal are on a good momentum right now and have far better quality than West ham. With Liverpool leading the table temporarily Arsenal will target to get the 3 points desperately and be on the front seat again on the table. Hammers are a tough opponent as they have some good players so Arsenal might have to be wary of their attacks.
West Ham will not be of any threat to the Gunners tonight and I believe that Arsenal won't want to lose this game or draw after playing a 1-1 draw against Liverpool knowing that Liverpool won their game and also topping the table, this game is going to be very hard for the visitors because the Gunners are going to make the defense of the visitors to be very busy.
West Ham haven't been that good this season and I feel they have been lucky to even get a win against Manchester United just because Man UTD are having it hard to play as a unit.
Arsenal need to win this game to go back to the top of the table as league leaders but for that to happen Arteta need to make his back line to be more aggressive because West Ham have guys who likes running through every defense they play against and I don't see the West Ham defense to be that strong to stop Arsenal's attackers.