Venus' swing volley is extremly powerful and wins her many points, in the Wimbledon 2001 finals she hit a swing volley winner when the ball was below the level of the net (she scooped the ball up at knee level!) !But sometimes she could miss one by miles when she gets over excited.
Hingis' swing volleys are not necessarily powerful but are extremly well placed and sometimes she steps in on a short ball to hit a swing volley instead of waiting for it to bounce which surprises her opponents... but her lack of power on her swing volleys sometimes allow her opponents to reach the ball, but she's ready at the net to hit the volley.
Tough choice between these 2 but I'd have to go with Hingis on this one...
-MARTINA HINGIS-Unconditional Love & Support, Always and Forever, Genius, Legend, StarAll the Best, Elena Dementieva, Anna Chakvetadze, Ana Ivanovic, Jelena Jankovic, Zheng Jie, Vera ZvonarevaKeep Fighting, Keep Believing
Novak "Nole" Djokovic