Quality --> XVID-80% --versus-- Transcoding DVD (with deep analysis)?

[SteveIT]

Hi there... I've been transcoding some video to:

-DVD-5 format (eg. 1,05 gig)
-XVID format (using AGK, 80% quality setting) (eg. 856 MB)

I've played both next to each other and didn't notice any difference really. My wife commented the XVID version seemed a little...