Credit Advantage
Usually defeat is defined as having nothing. Thus the more you have the further you are from losing and have more options and power to influence the game. This path to victory is about securing that much that even if applied crudely will be enough to bring the opponent down. On the other hand denying resources to your opponent means that there is that much less to destroy. Important indicators for credit advantage are the number of resource gatherers, the amount of credits and the number of resource crates controlled. A credit limited economy must often wait for enough credits to accumulate that the next planned thing can be started. A credit excess economy can afford to spur many back-up plans or simply grind the opposition down.
Measuring everything in resource efficency draws easy attention to how a player's credit advantage is developing. For example not measuring military success on the number of units killed but the resources that went into building the lost hp.
Focusing too much on resources might distract players from how the resources are applied. A 2000 L-crystal fleet of many fast aircraft is very different from a 2000 L-crystal fleet of few slow tanks. Also resources must be spent before they can benefit the player. Watch out that while your 1000 resource is sunk in RPs that the opponent 100 resource raider won't destroy them all. Also resources spent on things not needed do not further the players interests. These kind of issues can be taken into acount by using different metrics, for example the amount of resources units that are currently engaged in combat or moving to the frontlines or simply deducting the resource cost of idlers from total wealth.