Also, what bike is faster depends on what the terrain is like, even uphill. There is an advantage to having rear suspension even in climbing, especially if that climb is rooty and/or rocky.
This ^^^^ I remember reading a quote from Ned Overend where he said that if rear suspension only helped on he downhill he would have never adopted it. But it can make a huge difference on rooty, rocky or loose climbs. It isn't just control, it is traction. You can have the stiffest hardtail in the world. It won't help if your wheel is bouncing all over the place.