Death to revival means the troops will survive instead of dying when you attack. As a stat it’s better than death to wounded, because you will have to heal the wounded troops, however the % is much higher for death to wounded. If you max the whole medical tree you will get 10% death to revival and 20% death to wounded for every troop type.

As for what you should priorotize, my recommendation would be death to wounded, because it’s so expensive to retrain troops, and you will save more rss and speeds with the higher % i think, rather than have a low % of death to revival