Truck trend did the test a year or two (or three) ago. The Ford V10 held its own against Dodge and GM handily. The 6.8 won most of the empty drag races and beat the Dodge when loaded/pulling. The 8.1 did pull ahead of both when loaded. Fuel economy was within 1-2 mpg.

As with everything else, drive 'em both and see which one YOU like best.