R. v. Zachary Evans-Renaud 2012 PECA 21 gives a helpful summary of the standard of review on sentence appeals:
Standard of Review
 The standard of review to be applied by appellate courts in reviewing a sentence has been stated a number of times by the Supreme Court of Canada. Appellate courts are required to show deference to the manner in which a sentencing judge exercises his or her discretion within the framework of the principles and purposes of sentencing established in the Criminal Code.
 Appellate courts have been consistently informed that a variation in sentence should only be made if the court of appeal is convinced that the sentence is not fit. The court of appeal must determine if the sentencing judge applied wrong principles or if the sentence was clearly excessive or inadequate. Unreasonableness in the sentencing process involves the sentencing order falling outside the acceptable range of orders. See: R. v. Shropshire, 1995 CanLII 47 (SCC),  4 S.C.R. 227;  S.C.J. No. 52, at paras 47-50.
 In R. v. M. (C.A.), 1996, 105 C.C.C. (3d) 327,  1 S.C.R. 500, Chief Justice Lamer stated at paras 90-91:
 Put simply, absent an error in principle, failure to consider a relevant factor, or an overemphasis of the appropriate factors, a court of appeal should only intervene to vary a sentence imposed at trial if the sentence is demonstrably unfit.
 ... But in the absence of a full trial, where the offender has pleaded guilty to an offence and the sentencing judge has only enjoyed the benefit of oral and written sentencing submissions (as was the case in both Shropshire and this instance), the argument in favour of deference remains compelling. A sentencing judge still enjoys a position of advantage over an appellate judge in being able to directly assess the sentencing submissions of both the Crown and the offender. ...
 The law is clear that sentencing judges are permitted a substantial discretion in the imposition of sentence, both as regards duration of sentence and the type of sentence. See: R. v. Wozney, 2010 MBCA 115 (CanLII), 2010 MBCA 115, para. 35.