As
@Beltex has said, appeal decisions are a complete lottery. While I concur with his own observation that these are 2 extremes, there are a couple of things to note here.
There seems to be significant trends in the way the IAD rules. In cases of departed minors, I find the Western division to be the least forgiving. The Central Division is a flip of a coin, while the Eastern division has very good odds.
I think the good odds with the Eastern division largely has to do with their more "European" approach towards blame and their less cynical attitude. Member Neron, who decided the Obando case, was from the Eastern division. His comments in his judgement have been citied in various appeals over the years, but the Eastern division seems to hold it in especially high regard.
I think another very important thing to note is the lost appeal was a PRTD appeal, while the successful one was a Departure Order appeal.
Should a PRTD appeal be lost, the PR is not in any worse of situation than he/she was before. In comparison, in departure order appeals, there is a very significant element of hardship as a loss equates to the person needing to depart the country and leave behind his/her life. It also adds points to the establishment part of the H&C analysis. Assuming the person comes back to Canada, re-establishes him/herself, and keeps foreign travel to a minimum, and in general demonstrates that they have a life in Canada and are unlikely to leave, that in and of itself is a relatively good reason to look the other way. This element is simply not present in a PRTD appeal.
Another key thing to note is that even in the case of being removed as a minor, while common sense dictates that a PRTD application should be successful, the OP should be careful about his approach depending on place of residence.
What I have seen on this forum is the European offices, especially London for some reason, seem to be more liberal in issuing PRTD's than Asian/African offices.
However, IMO the best odds rest at the U.S. Canada land border.