Well, there is one advantage to Shadow Wasp Strike over Cut and Run--namely, if you miss with your Shadow Wasp Strike, you can use Elven Accuracy or the like to re-roll the whole attack instead of just half of it. If you have a 60% chance to hit and are using Elven Accuracy, then Cut and Run has a 64.8% chance of hitting twice and a 28.8% chance of hitting once, while Shadow Wasp Strike has an 84% chance of hitting.
Unfortunately, the fact that Cut and Run lets you add your Strength or Dexterity bonus to both hits means that Cut and Run still wins if you have at least a 12 in the relevant attribute. The quarry rules also favor Cut and Run--even though you only get to apply quarry damage once per round, you only need one hit in order to apply it, and your odds of scoring at least one hit are better with Cut and Run.
Still, I at least had to do a little math to confirm that Cut and Run was better... that's something, right?
(Also, there are a handful of critters with resistance to weapon damage. Against these, Shadow Wasp Strike is of course superior to Cut and Run. But unlike in 3E, those critters are few and far between.)