Most of the upgrades come from replacing a shuriken catapult with a shuriken cannon. This increases your range to 24” inches, gives you a extra shot, along with a S 6 punch. Beyond an increased chance to wound Vs. MEQ it gives you some light anti-tank and anti-monstrous creature options. There are so many places to upgrade it almost makes most of your Eldar army pumping out S 6 shots- some quick examples off the top of my head- vypers, wave serpents, guardians, war walkers, wraithlords, death jester, jetbikes, etc.
That S 6 makes a big difference, especially in unexpected situations. Personal example: a doubles tournament I was playing with Jawaballs as we faced off against an ork and daemon combined list. (First battle in the vid below.) At one point we were dealing with or knob bikers coming in for the kill as a greater daemon came in materializing right along our front line. With my seer council occupied with a soul grinder we faced an interesting choice- deal with the bikers or the daemon. Given the daemon’s high toughness I turned the shuriken cannons on my jetbikes and vypers on it bypassing its high toughness and gunning it down in one turn of shooting, while Jawaballs dropped on the ork nob bikers. In that instance if I didn’t have a bunch of S 6 weapons we probably would not have brought down said daemon and might have lost the game. Shuriken cannons fit really well into a Saim-Hann type build as the speed of the jetbikes and vypers makes hitting side or rear armor really easy- where S 6 can really cut through them.