When I lived in Seattle I commuted on a 3 speed + Coaster brake. I chose the coaster because it doesn't lose any braking power in the rain (unlike rim brakes) - which is important in a city with hills where it rains a lot. Using a front brake meant that I could use the coaster brake to slow down, but then bring the bike to stop with the front brake, allowing me to position the cranks for an easier start.
A front brake is also a good precaution anyway since if your chain breaks or slips off, or the coaster malfunctions for any reason, you can still safely stop the bike.
When I lived in Savannah, I used this old Murray which had a coaster brake:
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