You and your opponent are both using normal rubbers such as Sriver. You topspin loop the ball to your opponent, and he plays his stroke by moving his bat from near his knee to above his head, in a fairly typical topspin action. What type of speed and spin will be on the ball that is coming towards you?
Answer: The type of spin can vary all the way from a slow heavy topspin if your opponent has spun the ball without much forward motion, to a medium-fast loop with medium spin if he has spun the ball and hit through the ball about equally, to a very fast loop or drive with not very much spin if he has hit through the ball without spinning it much.
In this day and age of smooth grippy rubbers, most intermediate and advanced players will know what is happening instinctively when they are playing, and adjust accordingly. This type of topspin rally is what the many hours of training has prepared you for. It is an entirely predictable scenario - if you watch your opponent's stroke closely enough, you will know what spin and speed is on the ball coming towards you.
Now imagine that your opponent is playing with a long pimpled rubber. Once again, you topspin loop the ball to his forehand, and he uses the long pimpled side to play a stroke from his knee to his head, in a fairly typical topspin action. What type of speed and spin will be on the ball that is coming towards you?
Answer: The ball will be anywhere from a heavy backspin ball to a float ball, depending on the type of long pimples used and the type of contact made by your opponent. It will not be a topspin ball. Read on for the reasons why.