When making decisions on moral grounds, and regarding altruistic actions. For example, seeing a picture of a single child suffer tends to induce relatively more empathy than seeing a picture of a whole family or town suffer. (That’s why you predominantly see the former in charity ads.) With rational compassion, it would be rather the converse. Having empathy with a group one is close to (in thought/space/time) also tends to make people more willing to inflict harm on a group that is more removed from them, while rational compassion would try to avoid such a subjective bias.