Mizuno Wave Sky 8 vs Mizuno Wave Sky 9:
Which to Choose

These two are more evolution than reinvention, but the differences are real and they cut in a specific direction. The Sky 9 grows into a genuinely maximal shoe: its stack rises to 44 mm heel / 38 mm forefoot versus the Sky 8's 40.7 mm / 30.7 mm, with the biggest gain up front, which flattens the drop from 8 mm on the 8 to 6 mm on the 9. That extra forefoot foam, combined with a switch from the 8's dual-density Enerzy EVA to the 9's nitrogen-infused Enerzy NXT top layer over a firmer Enerzy carrier, is what gives the 9 its softer, more cloud-like landing. The trade-off is twofold. First, the 9 is heavier, at 295 g versus 277 g (men's US 9), so it feels like a bit more shoe underfoot. Second, and more surprising for a successor, the 9 is actually the less energetic ride: our cushioning score climbs from 5/6 to a maxed-out 6/6, but responsiveness drops from 4/6 to 3/6 — the newer foam absorbs impact beautifully but returns less pop than the 8's springier EVA when you try to roll through the stride. Everything else is essentially unchanged: both are stability-4/6 neutral platforms with wide, sidewalled bases and no plate, both sit in the same easy-training pace window, and neither wants to be pushed fast before the tall stack goes vague. The clearest practical shift is intended range — the 8 is happiest at 10K-to-half distances, while the deeper, softer 9 is comfortable stretching from the half out to a relaxed-effort marathon.