The more synonyms and phrase relations there are in it, the more the spinner will understand whatever content is thrown at it and the better the content it produces will be. Now that’s not specific to Spin Rewriter but I thought I’d throw in this as most people probably have no idea what a spinner does and then complain when a certain word is replaced with the wrong synonym (context-wise).
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.