Aiditorial Article Rewriter is the best article rewriter tool. Aiditorial Article Rewriter provides alot of options to customize the software. 

Basic is fine for the beginner article marketer. Pro however has many more features to save a bucket load of time and will also not show advertisements.

Both the Pro and Basic versions of Chimp Rewriter are contained in the same application. Upgrading or downgrading versions does not require any software to be installed or removed. 

A complete list of differences can be seen at

ChimpRewriter - Best Article Rewriter - helps rewrite your article in secondsChimpRewriter Article Rewriter checks for duplicate after you rewrite.