I think if you are just comparing the "speed" then yes it is similar. The difference is in the action most men put on the ball. The ladies tend not to put as many revolutions on the ball, but I would say that the speed of the ball going over the net is relatively similar. The action off the court is another thing...Right now I am watching the Semifinal match with Maria and Woz....
Maria is hitting a ton of winners, way more than I see in mens tennis. I mean compared to Roddick who rolls them in, Maria seems to be blasting and painting the lines (obviously can't do this all time). I know this discussion has been had before, but I really think negating the serve of course of mens tennis, that rally's may not be as far off as we are always quick to say - at least in this exact case when she is in god mode.
I also know mens tennis there is much less time to set up, since there is alot more spin. Regardless...