Rakan W range: 600, with a 250 effect radius
Riven E Range: 325
Riven W radius: 125/135
So Rakan can get to a target up 1000 units away, and then knock up anything in a 250 radius, for 1 second, and then instantly charm them for another 1-1.5 seconds.
Riven can only go 725 units, and then stun for .75 seconds if they are 125/135 units.
And if you want to count her knockup + flash, that's only 660 range with a 150-200 effect radius.
And did we mention that Rakan can then get back out after doing that with his dual 700 range shield dash?
Pretty significant difference there between these two cases.