Cross Platform – Being a Mac user I prefer when I can fire up a program locally. WordAi is web based and therefore works on Windows & Macs without issue (Linux as well). SpinnerChief III Ultimate has a Web Api that allows spinning from the web, but we did not have much luck with it, so at this time we consider SpinnerChief a Windows only application and therefore requires me to run it in a virtual Windows Machine using VMWare Fusion. This one is a hard one to call because clearly WordAi wins cross platform, but it doesn’t have all the extras that SpinnerChief offers.
SpinnerChief is designed to generate unique articles to provide content for websites and increase site traffic. It does this by spinning one article into multiple versions of itself, replacing certain words, phrases, and sentences with alternate versions of themselves. SpinnerChief can identify parts of speech, correct grammar errors, and use intelligent auto-replace methods until the article is both human-readable and passes Copyscape (a plagiarism checker). The SpinnerChief API allows developers to access SpinnerChief's functions from within other programs and can spin articles in 27 different languages.
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.