What are the differences between djay for iPad and djay for Mac?

They are basically the same, but djay for iPad is an application that has a GUI screen taking advantage of the touch panel, allowing tracks to be selected directly and DJ performances to be held intuitively by touching the screen, while djay for Mac is an application with a easy to understand GUI screen on which tracks can be displayed as lists, allowing for more full-blown DJ performances.

For details on "djay for iPad" and "djay for Mac", see the Algoriddim website.