DH - so using MPEG Streamclip, does the quality still degrade as much as if you ripped it using Handbrake?
You're comparing apples to oranges. Handbrake is used to convert a DVD's highly compressed and multiplexed VOB files into an even more compressed format: MPEG-4 (yet another delivery format).
DVDxDV and MPEG Streamclip will allow you to convert a DVD's VOB files into any number of editable OR delivery formats. Both offer good quality IF the original footage was decent and IF the first DVD encoding process wasn't too hard on it.
Quality is highly subjective. You're working with footage that's already taken a quality hit when compressed for DVD and attempting to expand that to a frame based format for editing (quality hit #2), then edit and probably recompress for a new DVD version (quality hit #3). Any time you compress video, information is thrown out .... and cannot be recovered when converting later. All of this means a loss of quality.
For editing purposes, go back to the original footage for any additional editing if quality is a prime issue.
-DH