The MVP is Most Valuable Player. Playing baseball includes many things, of which batting is a single aspect. Granted, it is probably the most important aspect of a position players game, but it is but one aspect.
Base running matters.
In both of those categories, Mike Trout of the Angels is head and shoulders above the output of Miguel Cabrera of the Tigers. If we are being honest about this, there really isn't a debate. A player who saves significant runs with his glove AND takes extra bases and turns singles into doubles 49 times has added value above and beyond his triple slash line.
Now, if we were talking about a VAST difference in triple slash line stats between Cabrera and Trout, then we'd have a debate. But we aren't.
Trout had a higher OBP by 6 points and lost 42 points of SLG to Miguel Cabrera. Overall, we're talking about Miggy leading Trout by 30+ points of OPS. That's a hot two week stretch away from being flip flopped. We could play another millennia and Cabrera couldn't field CF like Trout or add value on the bases like Trout.
If the award was the "best hitter" - then Miggy is a legitimate favorite. If the award is supposed to take into account all aspects of the game everyone is in line behind the 21-year old Trout, including the first triple crown winner since 1967.
To argue otherwise is to put your head in the sand and ignore whole swaths of the game of baseball.