The 70-300 VR is an AFS lens, and focuses adequately fast on pretty much all the newer Nikon bodies. Also, the 80-400 is a critically slow focusing lens. For that reasona alone, I have never traded my AFS 70-300 for the extra 100mm of the 80-400 (even though the extra 100mm would be gold for shooting outfielders in baseball).
As far as I'm concerned, the slow AF for moving subjects is a deal-breaker for me. I can't wait for an AFS update to this lens, but sadly, it will probably cost about $2,000, and be out of my price range.