The XS has an adjustment feature which gives you the ability to control the amount of resistance in the float region. The XE has a preset fixed resistance level. Note that Time's float resistance is not the same thing as Shimano's tension control. The difference is that Time decouples float resistance and release. Time pedals will release at angles set by position of the star on the cleats (13 deg or 17 deg depending on how they're oriented) and not based on the amount of reistance set in the float. Shimano pedals couple float, resistance and release thus by setting tension you set the threshold of release.