No, they wouldn't have to taste or smell either one to be sure. Quite simply, they could pick out each fruit just by feeling it.
Our sense of touch is a key part of the human experience. It's why we prefer to wear shirts or blouses made of silk instead of those made from burlap.
Not only that, touch is the only one of our five senses that covers our entire bodies. And we have lots of nerve endings all over waiting to give us this tactile feedback. Consider that your fingertips alone contain some 1,000 touch receptors - roughly 100 for each tip of each finger.
If you stop and think about it for a moment, you'll realize just how complex the sense of touch really is. It combines the feelings of hot and cold, rough and smooth, wet and dry, soft and hard, as well as pain and pleasure.
Now just imagine trying to put such a complex system into a sensor so small it could fit into the tip of a robot's "finger." No doubt that would a huge breakthrough.
For one thing, it would make robots far more "human"...
It would open up a whole new range of jobs for robots in industry, farming, and mining.
It could even usher in the day when a robot could learn to play the electric guitar in a way that rivals the late rock legend Jimi Hendrix. And it could certainly improve the quality of life for millions of amputees around the world.