Other article spinners also require that you enter your own custom synonyms manually or individually approve lists of potential synonyms as they are presented to you. This is another way of expecting you to do most of thinking, as opposed to expecting the software to be smart enough to instantly make judgment calls for you. Thus, one of Spinbot's main goals is to make the article spinning process as quick and painless as possible.
I think it is better to just come up with your own content. Most of those type of programs that are designed to make things easier, really just make things more difficult. You are right. The more you write, the more practice you get, and the better you’ll become. I have been writing for years myself, and I have never needed any content generation programs.
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.
If you have not used a spinner before then I would suggest that you first use something that require more human imput like The Best Spinner or Spinner Chief in order to understand the basic principles. However if you must go fully auto then I would suggest you go for Wicked Article Creator. I have it and understand it is similar to wordAI but a one off fee of $47.