On one hand, an unhardened Alistair is fragile minded, dependent on others, and fearful of becoming a king but is generally committed to his duties and unyieldingly serves his people to the end. On the other hand, hardened Alistair no longer fears becoming king, disapproves of your evil actions less, and puts his own needs before anyone else's, hence the dialogue option "Everyone's out for themselves. You should learn that." needed to harden him. So essentially he becomes more selfish and less apphrehensive when the Warden does bad things. So is it more preferable to harden Alistair or worse?