Selecting a Grand Company - based on aesthetics, player population, or class?

[Neptune]

And can we change our mind and switch?

-Do I pick the area I like the most?
-Do I pick the area with the best player population for doing Grand Company activities?
-Do I pick just the Grand Company that sells my class's gear, since it's available exclusively there?

If the player population shifts or another Grand Company starts selling gear for my class may I switch Grand Companies?

[Teknoman]

And can we change our mind and switch?

-Do I pick the area I like the most?
-Do I pick the area with the best player population for doing Grand Company activities?
-Do I pick just the Grand Company that sells my class's gear, since it's available exclusively there?

If the player population shifts or another Grand Company starts selling gear for my class may I switch Grand Companies?

I'd go with choice 1 or 3. I think we'll be able to switch at some point, but the devs have said that you'll be able to do regular Grand Company quests with others, regardless of affiliation, and may even receive bonuses.