Sadly.... Shiny Spears are better Skyweavers with the new Eldar Codex, they IMO (having play both many times in 8th) are equal to each other in the Index, where Skyweavers can move farther and still shoot and melee, even on turn one. Shiny Spears still with a 4++ has way more damage than Skyweavers (dbl if not triple damage).
But out of Reavers and Skyweavers? Skyweavers are leaps and bounds better than Reavers, yes Reavers are 3 models vs 2 models, but those 2 models are 4++ and -1 to hit with Shurikens.