Dumbledore is not saying Snape’s soul is disposable or less worthy than Draco’s. He is throwing himself on Snape’s mercy and asking if Snape thinks he might have what it takes to care for Dumbledore. Would he be able to kill for a protective reason, split his soul by killing, and then withstand the possibly fatal process of remorse that is the only way to reintegrate his soul? They can’t let Draco kill Dumbledore. In the unlikely event that he succeeded, he wouldn’t be able to recover.
