We believe any established tool satisfies atleast 80% of a user's requirements.
So how does the user decide between which tool to go with?
In a very modest effort we have created a simple grid containing some of our competitors
(e.g GoMockingbird, Balsamiq, iPlotz, Axure)
We start the grid by listing some important and some good to have features for MockupTiger.
You will find 80% match between features across all the products. But then some tools will help you do something very specific. So go with what is important and decide.