> And in some circumstances four-way stops flow more traffic.

There's no way that's true, is it? What circumstances would a four way stop sign allow for more traffic flow than a roundabout?

I'm pretty sure it's purely cost-cutting. Four way stop signs are extremely cheap compared to roundabouts. There's no other advantage that I can think of.

Roundabouts are safer (there is no opportunity for t-boning at a roundabout), faster and simpler to navigate than four way stop signs (a roundabout you just give way to people already on the roundabout, a four way stop sign requires you to keep track of who arrived first and then do a weird dance if you both arrived at the same time, and you still need to watch out for people attempting to go out of turn -- which is not possible with a roundabout)