Overflow location completely depends on where you are putting the tank in relation to the room.
If this is going against a wall with three sides visible, you might want to go internal corner if you want to push the tank as close to the wall as possible. Internal offset center against the back (or internal center against the back) might be good too if all three sides are equally visible.
If the tank is going into a wall, then external corner would maximize the interior space and be the most attractive when looking into the tank.
If you're going free standing with all sides visible, then center column might be a possibility, but I agree with Gresham that you'll need to consider aquascaping challenges with the column.