To declare that the defendant is to be vulnerable to future punishment can be, in itself, an impressive expression of the community's moral disapproval. At the same time, the conditional suspension of the punishment, whether it be a fine or term of imprisonment, can provide an environment favorable to rehabilitation, both by conveying to the defendant a sense of the community's confidence in his ability to live responsibly and by giving him a special incentive to do so. It would seem to follow that a suspended sentence with probation should be the peferred form of treatment, to be chosen always unless the circumstances plainly call for greater severity. - H.A. Hart, The Aims of the Criminal Law

It would seem that the judge should have the power to fix a minimum term, although the power should be used with caution, since its exercise will deprive the prisoner of an opportunity by his behavior in prison to justify an earlier parole.
Anarchical inequality in the sentences ...

? The creation of a new authority, with the single responsibility of equalizing sentences initially imposed, to the end of assuring that they reflect uniform concepts of degrees of blameworthiness.