The received wisdom is that InstantCopy offers the best quality. It also takes longest to transcode. The latest and greatest DVDShrink will probably give it a run for its money when it comes out of beta. Interestingly, Shrink, in its 'deep thought' mode, takes second longest to get the job done - clearly a correlation.
The author of DVDShrink somewhat surprisingly still appears unable to disable the discontinuity (layer-break) bit, so you still have to use IFOEdit to remove it manually if your particular setup hiccups when it runs into it.