I did quite a bit of research and experimenting with different programs and this is the resulting routine I use to rip and copy DVDs:
1) Have 'AnyDVD' running in the background. This removes ALL copy protection on the market basically and allows you to copy some discs ripping programs can't.
2) Rip DVD using 'DVD Decrypter' in File Mode.
3) Use 'DVDShrink' to analyse to the ripped content and you can decide what(if any) extras to keep, sound streams, subtitles, menues etc. The more extra unneeded crap you remove the less compression needed for the main movie. If after removing the extras it still requires more than 10% compression ( Compression Level 90% on DVDShrink) then I will not use DVDShrink but will go to step 4. Since I dump all extras and only keep Eng multichannel stream I can use DVDShrink for about 60%-70% of the DVDs I've copied.
4) By far the best encoder available is the 'CCE SP' codec (which costs $2000US for top version). However there are much cheaper but almost effective CCE codecs. To use these codecs you can use a program called 'DVD Rebuilder'. These are professional quality codecs and if more than 10% compression you can indeed see a large difference... the better display/TV you have the more you'll notice. This is kind of a complicated program to set-up and not nearly as simple to use as DVDShrink but the results are worth it.
3) If the DVD was rebuilt using DVDShrink it will have created an ISO which you can direct it to use DVD Decrypter to burn (you'll need Nero installed for this). If you've rebuilt the DVD using DVDRebuilder w/CCE then you'll have to use a program like 'ImgTool' to build the ISO then you can burn it with DVD Decrypter.
Simply search for these programs on Google on you'll find a WEALTH of information on how to use them and how to acquire them (try alt.binaries.dvd to 'try out' the programs that aren't free). Spending a few hours reading will ensure best results and save you frustration.
NO matter what anyone says there is NO single DVD copying program that does everything the best. Each have their strengths and weaknesses.
Hope I've helped as much as I've probably confused. hehe.