You'd think that was you know, his home club Barca.
I've love Pep but his post Barca jobs have proved he's basically the same as CR...go to the best club in the country or at least to the one with the most money, win something and proclaim yourself as taking on a great new challenge. Just as we'd joke about CR saying how going to Juve was a challenge, Pep came out and said the exact same thing, if he were to go to Juve next. That's 4 best leagues, but always gone to the best team with the most money.
Not a Pep fan boy but this is not exactly true.
1. Pep has build his Barça team. He was "given" a golden generation of La Masia but RM had more money then and at least as good if not a better team on paper. Remember we finished 18 points behind them a season before.
2. Bayern: sure, he went to the best team in BL but his goal was to win CL (which he failed to do). What made his job harder from the beggining was Heynckes winning a treble just before Pep took over. He didn't know this would happen though when he was announced in January 2013 (and he probably agreed to join Bayern already in summer 2012 before taking a sabatical year and there were even rumours he did that when he was still in his last season here) or maybe he would have second thoughts about joining Bayern. How can you improve (results-wise) a team that has just won a treble? IIRC Pep even admitted publicly he was supporting Dortmund to win that 2013 CL final so his job would be a bit easier.
3. City: in a season before Pep took over City almost missed on a CL spot (they've finished 4th with the same number of points than United and 15 points behind a champion Leicester). They've already had some players that become key in Pep's team but still needed to spend a lot of money for players who fit Pep's system. They've invested over 500m net in new player since 2016 though United is not far behind and we know how the results of both teams (in the league) were. What played in his favour was City's history and lower expectations (despite high investments) compared to Barça or Bayern. They've only won 4 league titles before Pep and he won them two consecutive ones for the first time in club history. So while fans were disappointed they didn't do more in the CL they were still happy with just winning the EPL. That's also one of the reasons why Pep feels more comfortable and happy in City and why he might stay there a year or two longer than in his previous clubs.
Now assuming Pep will go to Juve. He'll go back to those expectations he had here or in Bayern. After winning 8 consecutive scudettos Juve fans don't care about Serie A anymore (unless Inter/Lazio take the title away from them this season then they'll maybe want to win it more again next year), they want CL. So while Pep would go to the best team in the league his true competition would be other elite European clubs more than Serie A teams.
I know it will probably never happen but I think if Pep wants a serious challenge he should go to Bilbao (he was talking years ago he wants to coach them one day but it was probably just him being diplomatic) and try to make them a contender for La Liga title. This looks impossible on paper but even Valverde finished 4th with them a few years ago and now we'll soon have Barça entering post-Messi era and AM rebuilding after Simeone leaves. Valencia is not what they've used to be and other teams like Villarreal or Sevilla are also not consistent enough. So only RM looks like they have a bright future ahead but even they will have to move on from their old guard (Ramos, Modrić, Benz,...) eventually and we don't know if/how the younger players will do.
Bilbao have a very good academy for Pep to work with and develop and good enough finances they could steal a player or two away from Sociedad (Oyarzabal, Merino (still don't know why Bilbao didn't go more serious after him when he was available), Zubeldia, Zaldua and a very talented Barrenetxea) and could also bring back the likes of F.Llorente or Javi Martinez as a shorter-term solutions.