What, Arsenal are more inconsistent than Chelsea, is it really like that? Arsenal have 40 points and Chelsea have 36 points and also, currently Arsenal are second and Chelsea are fourth below Nottingham who also have 40 points. Thus, Chelsea is an inconsistent team compared to Arsenal and not the other way around. Indeed, previously Chelsea also had time to be in second place in the standings but anyway, over time Chelsea experienced inconsistency, until Arsenal and Nottingham managed to be above Chelsea. But still, Liverpool are still firmly at the top of the standings and the position of the top four, I'm sure there will still be changes over time, because maybe Manchester City will return to the top four, who knows.
Arsenal are only less consistent than themselves in two latest seasons but compares to Chelsea in this season, they are better in consistency. As you compared in their total points and ranks, Arsenal are better and it's unfair to say a better team with higher rank are less consistent in performances than a club at a lower rank.
Chelsea shown their good development and improvement but their fall recent weeks shows that they still have weakness and are not strong enough to compete with Liverpool for Premier League title in this season. Arsenal and Chelsea can compete for a second position in Premier League and they only can warm of a title race for a while, before failing it to Liverpool.
If Manchester City returns to top four, they will create pressure on Arsenal and Chelsea for a second position race.