Re: default production

    Before I get contact with any other civilization, I usually always build
    settlers first, and the first combat unit is an annoyance, but once I
    border a hostile civ, building a defensive unit is first on the list of
    priorities.

Except early in the game, I usually send a defensive unit (built in a
city with a barracks) along with the settlers.  It is safer, and seems
more efficient, so that the new city can use its limited production to
start building the improvements it needs to have.  Is that not the
best strategy?