City managers are hired (at least in my town) by elected non-professional middlemen. The city managers are hired guns from outside & not directly accountable to the people. The city council are a bunch of dilettantes who have other jobs & incomes, thus have divided interests & distractions.
Strong mayors are voted in, act as professionals, & actually rule. They are also responsible to the people.
I’m not sure which is better, which is worse.