I have no doubt that Robinson will be very exciting. But other than the fact that he is stronger, I'm not sure he brings more to the table than Leandro. Robinson's main value is that he is very athletic and a great leaper. But unless he makes a dramatic improvement from his college performance, has shown now point guard skills and limited outside shooting skills.
BTW, for the Suns to use Robinson they would have to make concerted effort to attack the basket more in the half court. That is Leandro's strength, but they don't really use it right now.