I liked dragonchild 's two points. I'd add that the number of defects can be completely arbitrary because a spec can leave out all the behavior the tickets/defects represent.

E.g., at my current gig, the specs for product features are usually sentence fragments. I kid you not. Asking for more details produces the response: "We don't have time for that right now." From that sentence fragment the dev is to intuit everything that needs to happen. My first two word ticket there ended up taking three CGIs, a bunch of rewritten PHP, a moved/rehosted website, a patched CPAN module, some JavaScript, and a 16 hour day to catch up with what was ostensibly a "gimme."

I do wish you could measure dev quality because I've seen a few idiots/slackers become managers and wreck dev teams or projects. I think time and money are the only real measures though. Mmmmm… No, posts on PerlMonks count too. If I were running a company there are at least 15 monks here I'd hire at any rate I could afford without so much as an interview. In fact, at least a couple of them have already responded in this thread. :)