Guys, I found this article in internet. Its Titled Tennis Backhand: A Biomechanical Analysis
Here is the link for the whole study. http://userwww.sfsu.edu/~evanthis/Tennis%20Study.htm
It shows that a 1hbh results in a greater ball velocity which is according to study is more efficient. But a 2hbh stroke has a more coordinated movement which allowed a greater stroking consistency, an often more preferable in tennis than the ball velocity of a 1hbh. This study supports what Tog is saying about the 2hbh. This topic doesnt imply which is better stroke but the effect on the ball of both strokes.
As a summary, here is the conclusion:
The two different tennis backhand strokes were proven to be more distinct than initially thought. Differences of the outcome and the movement organization were certainly evident in our study. The greater ball velocity and change in ball momentum that the one-handed tennis backhand generated was primarily a result of a greater force applied by the racket and a flatter racket hit with less topspin. Furthermore, the greater ball velocity/racket velocity ratio of the one-handed backhand suggests that the stroke was more efficient.
According to quantitative evidence in the kinematics and kinetics of the backhand strokes, the two-handed backhand was not as forceful as the one-handed backhand. However, the racket angular velocity analysis and the summation of forces data imply that it was a more coordinated movement. Consequently, the two-handed backhand must have allowed a greater stroking accuracy, which is often more preferable in tennis than ball velocity.
A good understanding of the mechanics of each backhand stroke is definitely valuable to anyone interested in tennis. The movement constraints however are also part biological, which explains why different individuals have different preferences. In deciding which one you should use, remember that one is not proved to be better than the other. Both maximal force output and maximal accuracy are necessary for a productive backhand stroke.