Too hard to say. I could say he's both. In his prime he was a very good writer. As of now not so much.
Ofcourse there are several outside factors that could be currently affecting his writing.
- Old Age, Family, Stress, Pressure to finish quicker and retire, Pressure to live up to his ( world building) hype and add even more things into the story....possibly even tired of the same story.
Without these factors, I bet Oda could be an excellent writer....as he shown thus far with pre timeskip. But I'm not gonna stand here and lie, saying current OP is good. Because it really isnt....