A single case may be published in multiple places, and so will have multiple citations. These are known as parallel citations. For more information on why there are parallel citations, see How cases are published.
The authorised report version should always be used when available.
The AGLC4 says which version should be used in Rule 2.2.2. in order of preference (see below table).
Supreme Court of Queensland Practice Direction 16/2013 directs parties appearing before the Court as to preferred citation and criteria for selection of authorities.
CLR, FCR, Qd R, NSWLR
Generalist unauthorised report
ALR, ALJR, FLR
Subject-specific unauthorised report
A Crim R, ACSR, IR, IPR
Unreported (medium neutral ctiation)
HCA, FCA, QSC, NSWSC
Unreported (no medium neutral citation)
See AGLC4 rule 2.3.2.
A list of authorised Australian law reports can be found at page 49 of the AGLC. Also in the AGLC, the Appendix "Law Report Abbreviations' at page 285 places an asterisk next to authorised, official or preferred series.