Now my explanation for choosing Portugal. I don't mind the traits too much, but (1) The Unique Building is useful. You build a lot of feitoria, which I will, and you have effectively a second Colossus. If you build both, as I will, every coastal city will have huge commerce.
(2) The Unique Unit is great. You can effectively invade civilizations on other continents or take every barbarian city that you find while your carracks explore the world, as soon as you get Optics. Given how long it takes to get Astronomy, this can be a huge advantage. It won't help much on Pangaea, but it'll be a killer on Archipelago or Terra.