Thanks for the great article and breakdown, Joe!

I’m curious about your definition of fidelity, as fidelity can be a description of high visual fidelity, and/or interactive fidelity, sometimes separately. For example, you might get the animation qualities modelled in monochrome but temporally accurate, or you can describe them with high visual fidelity, the exact colours and transparencies, but static. of course there i also both temporal and visual accuracy. You appear to be concentrating on visual fidelity.

Also, I’ surprise Axure is so far along the fidelity line as it can be a very good, quick lo-fi tool if you have your templates and libraries ready for that. I’d call that far lower fidelity than a visually accurate version created with inVision.

Maybe the apps don’t have a specific location, but an arc of a range of fidelities it can help in. I get the feeling the slow/fast dimension is more about how long it takes to learn the tool and not treating each tool as something that once learned, can become fast to operate in.

And finally, I found, to my horror one day during testing that UXpin couldn’t render adequately in IE, my target browser and (arguably) a prime target browser. It took me to JustInMind, a far more detailed and superior product to UXPin, with a far better render base. Another excellent product that has matured well and should be here, among, UxPin, Axure, and Xd (Xd is fast???).

But, no doubt, there is no definitive answer to this question, as these comments will attest to, and getting them all out here is an excellent way to expose the qualities of each.