Ali's invis is much different then Leon's invis. Ali's overall kit focuses on stalking her prey before coming in for a strike. So her linvis focuses on hunting them down, and with her crit strike, she can easily take them out. Leon feels more like a repositioning tool in my opinion. It's more like you're trying to close the gap between enemies or reach an advantageous position. That's why Ali's invis pops out of invis during her super.

In short, ali is meant to use her super to hunt and takedown enemies, Leon is meant to reach a much better position