Agree with Texan that backspin does help the ball carry and is ideal on most hits. But...
It is not ideal to swing down in order to create the spin. Any carry that is added will be negated by the lack of force produced by swinging down.
A ball should be met squarely to produce the maximum amount of force. In other words, if you want to produce force in a 10 degree upward angle (line drive over the SS head), the bat should collide with the ball at that 10 degree upward angle.
Picture hitting a forehand in tennis. If your goal was to hit the ball at maximum force, you would meet the ball squarely and direct the racket in the line of intended flight (just over the top of the net, slightly up). If your goal is to create backspin, you swing down and "cut" the ball. Correct me if I'm wrong, but this is a finesse shot. The more the racket moves away from the intended flight (racket going down, ball going up), the less force is transferred to the ball.
Besides all this, according to Robert Adair's "The Physics of Baseball", the maximum amount that backspin will add is 15 feet to a 400 ft fly ball. So the maximum amount that this magical backspin can "carry" a ball is less than 4% when compared to a ball with no spin. I've heard instructors tell kids that backspin will add over 100 feet!
Play this clip frame by frame: http://www.youthbaseballcoaching.com/mpg/nomar3.mpeg
Look at the the frames right before contact until the ball leaves the screen. The ball and the bat are travelling at the exact same (upward) angle through the hitting zone. This is the case in over 90% of line drives/home runs in MLB. This is more important to driving a ball than attempting to produce spin.