They all matter.
I would personally place varying amounts of value on their lives depending on what they are fighting for.
To me at least, every life no matter what you do with it has value. But a life used fighting for imperialism or a life used fighting for the defense of a repressive dictatorial system is of lesser value to the world than a life given fighting against imperialism or a life given fighting against a repressive dictatorial system.
So the short answer is yes their lives matter, but some lives given in battle are worth more than others.
“Wherever death may surprise us, it will be welcome, provided that our battle cry, reaches some receptive ear, that another hand stretch out to take up weapons, and that other men come forward to intone our funeral dirge with the staccato of machine guns and new cries of battle and victory.” -- Ernesto "CHE" Guevara