It is vital to be aware that each individual serve has its own recovery time in some cases much longer than others have. With the axe service for example where it is necessary to bend the legs and serve from a low stance, it may be difficult to recover for the next ball if the return is long and fast. With the backhand serve often the action of the arm and the body brings the player back automatically to the ready stance, so that he or she is in a good position to take advantage of the return ball.
We may only be talking about tenths of a second, but our sport is so fast nowadays that every fraction is important. Another consideration is that the time element can be further complicated by tactical considerations. If you for example combine a slow recovery serve from a bad service position, from which it is difficult for you to recover quickly, you risk a quick return which can leave you stranded. Similarly if you serve to an opponent’s strength, long to the forehand corner for example, you risk a strong return, regardless of how good or how spinny your serve may be!
Another consideration is which serves can give you a better tactical advantage. With some it is much easier to vary direction and placement and you can create a variety of spin and length with the same or very similar actions. It is also important to use serves, which allow you to play to your own strengths on the third ball.