Liverpool vs Arsenal match won't just show the team that did a good job in the transfer market but it will show the team with the chances of getting the league title their season because both teams are title contenders but Liverpool being the defending champions should have an edge over Arsenal because of their consistency last season and their current squad this season. Newcastle United is a better team than Manchester United that Arsenal defeated their is why I think Liverpool has more advantage in the match.
Exactly this is crucial test for both teams. Win would be huge boost and prove they are serious title contenders. You argue that Liverpool as defending champions have advantage because of their experience and consistent form. Your idea that since Arsenal beat Manchester United and you think Newcastle is better than Manchester United then Liverpool should be even better than Arsenal is creative way to look at it. This match is chance for Liverpool to show their dominance and for Arsenal to prove they can challenge best.