Dave Cameron has an interesting article at Fangraphs, Trout and Cabrera: Here We Go Again, which is well worth the read. He concludes that Trout’s the better player, but, I think the stats make a strong argument for Cabrera as the slightly more valuable player so far—
I’m a big fan of RE24 & WPA. If you’re not familiar with those stats, you should read Get To Know: RE24 and Get to Know: WPA. I believe they are two of the most telling statistics. I don’t believe RBI totals say much about a batter, but that their RBI % actually tells us something.