There are probably hundreds of data feed tools in the world. All tools are able to create data feeds according to the feed specifications of shopping channels. Most of them just offer an export of the product data to a shopping channel (in the right format), with no or limited functionality to optimize. The advantage of these tools is that they are free or cheap.
Only a small number of tools offer ‘full functionality’ that enable merchants to optimize their feed in such a way that it will really improve his performance.
Acquisio, a leading digital advertising solution, published a market study in their blog post 10 Tips to Pick The Best Shopping Data Feed Tool