Based on whichever city you pick, your overall stats (that are in the middle) change. For example, if one of the cities has a green “culture” slider then your overall culture stat will increase if you choose that city. In the middle you can see how much culture or any other stat you already have so if you already have a lot of culture then you should probably pick the other city since you don’t need to boost your culture stat any more.
One thing you should do is optimize your overall population stat because if it gets too low then all your people die.