Love can be more demanding. After all one can be compassionate towards someone, understand their feelings, "feel with" him, but just not care for him much. Applying the term LOVE may imply requiring yourself not only to understand him, but to actively, well, love him. Just make sure it's really HIM that you are loving, not an idealized abstraction.[via A Progressive Christian]
If you interpret "compassion" in a manner like mercy, you might import a hierarchical view of feeling compassionate to those beneath you.