A benevolent dictator does have its advantages. For example being able to determine a culture until it's proven and critical mass makes it unlikely to change. It's comparable to the eternal September problem.

Say some 'hippies' try to bootstrap a city that's very walkable and people flock to it because they want to live in such a city. But it takes a while to get used to a new situation and during that time it's very easy to say "I like to walk to the shops, but I'm used to doing my groceries once a week, so allow me to use my car for that." Before you know the 'short-sighted yuppies' overwhelm the 'stubborn hippies' and cars are allowed everywhere one exception at a time.

The biggest disadvantages of a dictator are overcome by being able to move easily and the city being part of the larger legal framework of the country it's in.

Multiple of both types would be nice to have to see how they turn out. If you are not locking people in, the amount of dystopia that such a city could support should be minimal.