200-400 VR or 200-400 VR II

I want to get a 200-400 lens and can get a used VR I one in mint condition for $1021 less than the VR II new. Is it worth the extra money to get the VR II. I shoot nature and want to shoot sometimes hand held with this lens. Other times on a tripod with the sidekick. I really am wanting to get the fastest focusing speed and wondering if VR II is going to be that much faster.
Any help?
Gordon