If you slide with proper timing across a room, it's just as fast as sprinting would be across that same room. During the slide you'll be off radar though, causing a blip only when you stand back up and initiate the next slide. The radar will ping in the same cadence that an invis player does when sprinting. For short distances, like to get behind cover or move out of cover, sliding is faster than sprinting because almost all of the movement is in the starting 90% of the animation. The reason sprinting ends up tying a slide over long distances is because you slow down right at the end of a slide and have to stand up to start the next sprint.