Whats difference between the free and the paid?

So where is the list that tells you the difference between the free and the paid? I usually like to see at a glance what this is with software offerings that have a free and paid version so I can make the quickest informed judgement as to how it will work for me. I see a zillion features and copy on the plugin page and sales page, LOL but nothing is telling me what the difference is? How can I make an informed decision without wasting my time experimenting with the plugin trying to find out if its going to suit my needs?