Honestly I don't think these teams are really equal. Because that was the Europa League before anything else. Arsenal wouldn't show the same performance there and in the Champions League. The Champions League is the most prestigious tournament in Europe and I will be expecting Arsenal to care about it the same as the Premier League.
Therefore I think Arsenal will win their home game against PSV by at least two goals. Maybe the game in Netherlands would be tougher but I still expect Arsenal to play way better than the last game between them there. Arsenal can collect 6 points against PSV in my opinion.
The problem is that when we are talking about European competitions, league games do not matter. Arsenal was already a better team than PSV Last season and they lost, which means that they are still a better team today and could lose as well. I am not saying that they will, I am saying that the possibility is there and it's not impossible.
This is why I believe that it's hard to bet on those type of things, like European competitions feels so different from the league ones. The result is not the same in both of them and you get to see something that is a bit different. The clearest example could be how Sevilla played so badly last year, and they ended up winning the europa league, beating so many big clubs as well.