gpg --gen-random quality level: is higher "better"?
This is a really hard question to answer. The definitive answer can only be found in the source code of gpg. However I can still answer your question using a mail I found (from 2013, details may have changed).




  Is 2 "better" (i.e. more random) than 0?


Yes, 2 is "better" than 0 and 1.
As per the linked mail the quality level determines the number of bytes being read from /dev/urandom and /dev/random for answering the query.

As it appears in the mail 0 and 1 are actually the same (this may have changed by now) and gpg will just answer your query with the requested amount of fresh bytes from /dev/urandom.

2 however is different. It uses /dev/random, meaning you have higher guarantees concerning the quality and entropy of the output (as you may have to wait some time, if this trade-off is actually worth it is another question). And more importantly it requests significantly more bytes from /dev/random than you query, namely nearly 19x as many and post-processes them somehow. So the entropy of the result is high even if /dev/random doesn't provide you with high-quality random bytes.