WAR is a needless complication in the case for Trout, which can easily be made in plain language.
Mike Trout hit .329/.399/.564 in 639 PA. Miguel Cabrera hit .330/.393/.606 in 697 PA. These lines are not all that different, though Cabrera had more power and more PA. Cabrera was the better hitter, but not by a large margin.
On to the non-hitting aspects of the game. Sometimes the difference between Trout and Cabrera is presented in a manner that suggests "Cabrera is a slow, large guy, so just about any player will be better than him." This is probably true, but that sells Trout short. Trout was easily the best baserunner in the majors this year, stealing 49 bases at a 90% success rate. I'm fairly certain that the last time anyone stole 40+ bases at 90% success was Willy Taveras in 2008. This helped Trout lead the majors in runs scored, with 129. That's the second-highest total since 2007 (Granderson in 2009). Remember that Trout only played in 139 games due to the Angels gaming his service time or whatever was going on in April.
Defensively, just for the hell of it, grant that Miguel Cabrera is at best an average 3B. Trout is easily one of the top CFs in the game. Everyone's seen the highlights; this isn't a case where one would need to reference any defensive metrics, so it doesn't matter if one trusts those or not. Trout is clearly superior by a wide margin.
Personally, I have a very hard time taking the playoff argument seriously. The Tigers were not better than the Angels. Their record was worse, their run differential was worse, their schedule was easier. The Tigers made the playoffs because they played in a division with Kansas City, Minnesota, and Cleveland as opposed to Oakland and Texas. Cabrera didn't have anything to do with that.
I guess one could give Cabrera a slight bonus for AVG/HR/RBI. I personally don't care, especially in the MVP discussion, because this depends on how the rest of the league performed. Cabrera hit better in 2011 than he did in 2012.
In sum: if you have a great CF with elite baserunning skills, would you ever want to transform him into a lumbering 3B just to gain a little power? For the last ten years, all we hear is that statistically-oriented folks are fixated on OBP and don't account for all the things that don't show up in the top of the box score (or anywhere in the box score at all). Trout and Cabrera were just about the same hitter. One stole bases with ease, one went first-to-third on singles, one played superior defense at a premium position. One of these players did the little things better than almost anyone else in the game. The other did no little things whatsoever.