The biggest problem with broad judicial discretion is that you get wildly varying outcomes with identical facts depending on which judge you get and even what kind of mood he's in.
If anything the system still has too much discretion (in the hands of police and prosecutors) that lead predictably to discriminatory outcomes.
The problem with restricting judicial discretion is that a judge always has a living breathing person in front of him or her, and a sentencing committee never does. This leads to inflated sentences across the board.
If anything the system still has too much discretion (in the hands of police and prosecutors) that lead predictably to discriminatory outcomes.