This depends on the writer. You should try both ways to figure out what is the best for you.
One source for this redrafting concept is Dean Wesley Smith (don't miss the second part). Smith distinguishes "rewriting" (fixing a draft) and "redrafting" (start from scratch). His main issue against rewriting is, that most authors tend to rewrite to death and he has a point here. That's why you have to compare your rewrites with the original text (and let others compare them) to not fall into this trap. If you revised the originality out of your text, you are in trouble.
But nonetheless I suggest to rewrite your draft, if you are a beginner. Smith tells you, that you shouldn't do it, but I guess he did it in the past and he learnt his lesson. And that's my point. If you haven't done it, if you have not experienced when a rewrite is an improvement and when it is written to death, you cannot make the choice, if redrafting or rewriting suits you better.
Try both concepts out and keep in mind what Smith says over and over again: No writer is the same.