Man City have been building their squad and spending money year after year just so they could compete well in both leagues. You can't really say which team has a better form since City also defeated Arsenal in their last match. We'll see how things go from here but my point remains that 5 points ahead with 11 games left doesn't make the Gunners too far ahead. They could also choke. Remember that they are also competing in the Europa League and that could affect their squad too.
Honestly it is even a shame at this point that they haven't won a UCL to this day. They have been basically dominating the premier league every single year, either they won it mostly, or rarely lost it once or twice I think and that still is a big deal for them because they should have won it those times too but even with that, Liverpool at least has a UCL title they can boast about, whereas City has none. They were better than most teams in the world at some years and yet they still lost.
Some of their players grew tired of this and now they are quite old, I bet that they will get rid of some of the players, already started to, and that's an issue, either they win it now, or they will need to rebuild the team with younger stars.
You know the UCL competition is different from the English Premier League. In the Champions League you will see strong teams that are from different league, the champions league is not that easy to win. PSG has the likes of Messi, Neymar and Mbappe but yet they still find it difficult to win the Champions league. This same PSG is the best team in the French league, so I think Manchester City being the best team in the English Premier League does not give them a guarantee they must win champions league. I believe as winning the champions league is a priority for them they will surely have it anytime soon, because they are working towards it .