The advantages of de-fragging a rotating drive are obvious, but an SSD?
Defragging SSDs is an utterly pointless activity as seek times exactly the same for any data byte. The choice of your SSD drive (and thus its associated firmware) will have a much greater effect on performance.
Defragging slow (5400rpm or 7200rpm) PC/Laptop drives is also a somewhat questionable activity as there are probably many other things you could do to improve your performance before reaching defragging.