Number of trees and harvestable resources shall be the 0th factor. Everything else seems only an add-on.
If you have sth. like 5 trees nearby, you can just chop them up with the free builder to make a new settler, and also have a lot of additional hammers that help you build up military, monument or campus.
That is said, if you settler among trees, basically you spend a settler, you get a city, a new settler, and a lot of other productions.
This means you get those productions plus the city for free.