WTA has bigger swing on FH and BH - examples: Wozniacki and Danara Safina - they take racket higher and further back than most ATP pros. ATP has more compact FH swing - examples: Federer, Agassi and Ferrer. Henin was an exception as others have noted, she proved you do not have to have a huge FH back swing or loop to generate loads of pace and spin.
I think WTA players might learn bigger swings to generate pace and spin when they are juniors and need the big swing to hit the ball hard and/or deep. Personally, I think it is a detriment once they are on WTA as they have less time to swing and too much racket head movement is just more things to go wrong.
Some ATP players do use big swings too - example: Soderling had a huge FH swing.