i still think dvd shrink has better quality, but here's what i do for the absolute best quality you can get out of shrink:
use clonedvd in DL mode (no transcoding/compression) and remove all extra audio tracks and titlesets that i do not want. save this to hard disk.
i think use that folder and shrink it to SL size with dvd shrink and backup as full disc. that way i don't lose menus by messing around with settings in shrink.
then i burn it with ImgBurn or clonedvd again.
it sounds out there, but if you like how clonedvd2 can edit while keeping menus and you like how dvd shrink transcodes with deep analysis and its other advanced settings, then it's a great way to go.
i only do this on discs that require more than 20% compression (ie at lower than 80%) otherwise, you're right...the difference is negligible and not worth the time investment.