Legal Aid, Sentencing and Punishment of Offenders Bill

Will the right hon. and learned Gentleman explain the practical difference between an offender who is given an IPP for, say, a minimum tariff of five years, who will then be released by the Parole Board on proof of meeting certain conditions, and someone who is given a discretionary life sentence with a tariff of five years who is released by the Parole Board on exactly the same conditions? What is the difference?