You can now see the valuation of the rival colonies on the top bar and their exact value is also shown on the relations panel after the contact with them has been made. These updates make it easier to decide with whom you need to have good relations with.
During the war It also helps to see how much value they have left. By destroying enough of their real estate you can achieve the economic victory even before they are completely swept away.
Also, the peace making has been improved. The weaker colonies agree to peace easier than stronger colonies and you can see during the negotiation whether the deal you are proposing will be enough for peace.