The difference lies in the spin/pace ratio, a flatter stroke travelling at a higher speed relatively to its spin.
To get a loopier stroke, players swing more vertically and meet the ball with a greater degree of closure at impact; to hit flatter, they keep the swing more horizontal and present a less severely closed face at impact. But if you look at Federer, while he seems to be hitting fairly flat most of the time, he's still hitting at spin rates in the vicinity of 2500 rpm on average. In truth, he hits more top spin on his flat strokes than most pros hit on their loopier balls!
The point is that top spin should be a tool to increase your control over your strokes: to tame the heat of a 70-80 mph forehand during rallies, you need a sick amount of top spin... but if you own spin production, you also own your shot and it will stay in time, after time, after time.
“For most Americans, economic growth is a spectator sport.” -P.R. Krugman
Last edited by 10isfreak : 02-12-2013 at 07:02 AM.
Reason: Additional details