It is also very helpful for people who struggle with the English language in general and writing in particular. A free article spinner or paraphrase tool makes it easier for them to get new content with minimal effort. The quality of content created with article rewriter is close to human written content if not equally good. To ensure the quality, you can edit content to fix any errors.
Conclusion, if it boils down to speed, money and most readable spun content SpinnerChief Ultimate is what you want. If you’ve just got to have a web based solutions then WordAi is what you want. Remember we are using the cream of the crop here Word Ai Turing Edition and Spinner Chief III Ultimate. I believe the majority of users will opt for SpinnerChief Ultimate over WordAi Turning due to WordAi’s cost.

Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.