Burn quality check and compression ratios


I have an NEC 3500A and I was wondering what software/tools I can use to check the quality of burns after the process is completed.

Also, when backing up a movie I try to include as many of the original features as possible. I try to keep both the DTS and DD 5.1 track, the english sub-titles, extras and directors commentary. My question is if the compression ratio shows 50% in DvdShrink, just how bad is the quality of the resulting copy??? In your opinions, what is the minimum compression ratio I should strive for for the main movie??

For example dvdinfopro, for quality checks.
For compression, personally for me not more than 30%, better lower.
50% reducing increases quality a lot, you’ll be able to see this on fast
movements etc. …