My family tends to play with the 5-6 player expansion with only four players, which I think tends to mitigate your mentioned issue somewhat; on the other hand,

My family tends to play with the 5-6 player expansion with only four players, which I think tends to mitigate your mentioned issue somewhat; on the other hand, having that much space also leads to a lot of 'solo play', where you don't need to trade as much as everyone can generally get the resources they need and you're just waiting for the resources. The expansion-with-four-players certainly feels less cut-throat/competitive, for good or bad.