I've used MoboPlayer, VPlayer, MX Video Player, DoubleTwist, Dice player and others and even on videos viewed on the SD card or USB 500GB external disk, there is mostly considerable 'stuttering' on playback and some times even picture breakup.
I have just read there is a video player call BSPlayer Lite which has been available on the Android market for some time.
I installed it on my Android box and it's made a noticeable difference in playback on HD videos, both streamed from my NAS via Ethernet using SW (.vob, .mp4, .mkv) or locally using HW acceleration (.mp4, .mkv)
BSPlayer Lite is not the pill to cure all ills, but it's certainly improved video playback on my FV-1 Android TV box beyond anything any of the other above listed video players have done. Viewing a 720p movie with smooth playback and audio sync have just become a reality for me and my 1GHz ARMv7 PowerVR SGX540 Android box.
So this is just a heads up for anyone looking for a video player that 'MAY' provide improvements in playback over their existing video player.