That's not remotely true, and only makes sense if go by the notion 'they both spent a lot' without looking at actual figures or looking at recent title wins and the players they had for those wins.
I've done the calculations based off of transfermarket multiple times but Pep's spent something like £150m-£200m more than Mourinho since they both took over as managers.
City's last PL win pre-pep was 2 years before he took over - in 13/14. Since then we've only finished in the top 4 once - LVG's first season, until last season, whereas City have finished top 4 every season since. It is true that Pep is making better use of his squad, and imo in general he's a better manager with a better philosophy, but he is benefiting massively from the fact City already had players like KDB, Aguero, Silva and Sterling already in his squad - meaning he could focus instead on plugging the gaps in his defence with the bulk of his spending - Walker, Ederson, Mendy, Stones, Laporte at £50m each, whereas our defensive spending has been Bailly, Lindelof and Dalot at £30m, £30m, and £20m each - that's £250m vs £80m.
The biggest single benefit that Pep had is that due to the price inflation in the mid 2010s, if he wanted to sign Aguero, Silva, Sterling or KDB, he'd have been looking at £70m-£80m each. Our attack in comparison when Pep/Mou took over was Rooney, Mata, Lingard, Rashford and Martial - aside from Martial I'd struggle to price any of those over £30m at the time. Mourinho started off well with Pogba, Mikhi, Zlatan etc, but he's not really a long-term manager so the wheels have started to come off already, but Pep and Mou in terms of spending and squads aren't equal at all. Though I do accept Mou should be doing a lot better, and frankly imo should be sacked.