Board bonuses are highly concentrated in NE. By not selecting there during random selection, you are "hoping" the other players do select the NE and fight back in forth while you sweep through the rest of the map unopposed. But if one player does end up with the NE to themselves to start, they will win. I don't like leaving so much of my fate in the hands of the territory selection phase. I would just avoid the random selection mode altogether for these reasons, although the imbalance effects the other modes as well.