@ByeByePoly Lets just make one fact straight before we discuss this further so
@Curious doesn't missunderstand and claim that someone hits with spin and not COMPLETELY FLAT.
EVERY BALL has spin in tennis, there is not a single ball that is hit in such a way that it has completely zero spin and is completely static in the air without rotating at all in any direction.
But when someone says a heavy ball vs a flat ball, they generally mean a ball that is hit with alot of topspin vs a ball that does not have alot of topspin.
The average WTA player averages around 1000-1500rpm
Comparing that to the men, Federer and Nadal average around 3000-3500rpm
The difference is IMMENSE, and not only that, women also hit more flat trajectories because they hit more INTO the ball, and the flatter the trajectory the less the spin will have an effect on the ball and explode into you because the ball travels into you faster before the bounce.
Its like if you hit a fairly flat ball with 1000rpm and then hit the ball in an extremely upward loopy path with 1000rpm, the first ball would have alot of incoming speed and the spin would have almost no effect, but the second ball would not have alot of incoming speed towards you and would also drop down at a more steep angle, so the ball would grab the surface more and explode into you.
Men generally hit a higher arc and much more topspin, tho even their lower flatter arcs have more spin than ladies.
Ladies hit low over the net and not alot of topspin, unless they hit angles.
The WTA ball will come towards you straight pretty fast and skid through the court.
The ATP ball will come towards you fast but will DIP down much more at the last second and explode into you and jump higher.