If you don't have a good drive and a clean disc you may get skipping/jitter and thus possibly never get a AR or CueTools DB match. (CTDB has parity records that can be used to repair some small errors.) This is the point of the elaborate re-read stuff Exact Audio Copy or cdparanoia does. Though even with a good drive you ought to be using a tool that checks for C2 errors, and that won't necessarily catch everything; error correction and detection is always probabilistic.

Also not everything is in AR/CTDB. Maybe 3% of the 1000+ CDs I've ripped had no records yet, though I do tend towards the obscure. I rip these again with EAC, which is set up to automatically do CTDB submission. (Usually I'm using the redumper tool which has some specialized features.)

Without external verification it's best to dump it twice and ensure they're bit equal, preferably with a different drive to minimize error correlation.