I use Spinner Chief service, because it is able to rewrite content automatically, it doesn’t make load of mistakes that other spinners do, and it is much cheaper and it takes under 10 seconds to rewrite a 400–500 word article. And after reading the article you sometimes need a few minor edits which can be done on their spintax editor. I guess it is cheap because it is a new tool, but I took the advantage of it and get it for a low price. It is also nice because everyone can try it out for free.
Spin Rewriter integrates with almost any SEO software. This allows you to post high quality articles quickly and easily. The only drawback is that you only get something like 300 API requests every 24 hours. You can quickly burn through this if you’re doing multiple campaigns. The developer does not currently offer a plan for heavy API users but maybe they will in the future.