I don't think you can put a number on Defense, Defense is ore about field placement and scouting.
I agree that it's difficult to put an exact value on, but to say it's more about positioning and scouting is ridiculous. That's part of it, but it's a gross oversimplification. But, whether or not we can gauge the exact value in "wins" is irrelevant in this case, because Trout is by all accounts (eye-test, scouting and advanced metrics) an ELITE CF while Cabrera is a well below-average 3B.
is Trout Defense worth 2.5 wins better than Miggy's bat?
I don't know why we're comparing Trout's glove to Miggy's bat. I'll say that the gap between them on defense is much bigger than the gap between them on offense.
I'll give you the basestealing but I'd like to think Miggy's 20 odd more XBH evens that out.
Cabrera has 64 more Total Bases. But Trout's 42 more steals cut away a lot of that gap...and his taking of extra bases combined with Cabrera's inability to do the same certainly makes up the other 22 bases.
Looking at the Baseball Prospectus baserunning metrics, Trout has been worth 10.1 runs while Cabrera has been worth -5.2
Tens runs is generally equal to a win...so there's 1.5 wins in Trout's favor.
Cano has a higher WAR than Miggy, by no means Cano is having the type of season WAR is making it out to be. WAR doesn't even take into account Cano's Stupid baserunning.
Cano is having a fukking great season...but he has a higher WAR because of DEFENSE. Cabrera leads in oWAR (offensive WAR) 7.0-5.2...but again, defense matters. And yes, Baseball-Reference factors in baserunning when calculating WAR, and yes Cano's is negative.