Well you can copy to a DL disc if you'd like, this will retain the exact quality of the original disc. However, discs are more expensive, it's trickier to get a good burn, and Verbatim is basically the only option worth using (CMC is good with some burners but it can be very dependant on the burner). For a DL copy, just use DVD Decrypter (not DVDFab Decrypter), 'Mode-ISO-Read' will copy the disc to your hard drive, 'Mode-ISO-Write' will write the disc. Some of the new DVDs released in the last year or so will need something else like RipIt4Me to be copied because of their newer copyright protection.
What I would suggest is compressing them to fit to a Single Layer DVD. Rip the DVD to your hard drive with RipIt4Me. When it's done you can shrink it using DVD Shrink, and when you click the 'backup' button in DVD Shrink select to output as an .ISO image. Then burn it with ImgBurn (or DVD Decrypter, which is basically an older version of ImgBurn).