The latter, i.e. they are just two different ways to convert the Klingon word to English spelling -- one takes the usual transcription, the other tries to render the sounds with approximately close English letters, with a sci-fi apostrophe for extra flavour.
Compare, perhaps, czar and tsar which mean the same thing and are also simply two different ways to write the same Slavic word with English letters.
The official difference is that quv is "personal honor, earned by one's behavior" and batlh is "general, philosophical concept, associated with integrity". Though I prefer to word it as quv is the recognition that others give you and batlh is how you act to earn that recognition. So it would be possible to be recognized for false quv when you haven't really acted with batlh and it is also possible to act with batlh, but never receive quv recognized by your peers.