Having spent quite some time on both.
Two pretty different skis.
Blends are soft, fun, more of a play-ski. They wont charge in the same way and require more finesse while skiing in crappy conditions. They still float, and carve really nicely. Amazing ski, but after they changed the flex i wouldn't really call them all mtn skis anymore.
Watchlifes are stiffer and something that can go anywhere. They are poppy and energetic but not playful and buttery like the blends.
Also fuck surfaces durability.
And why go 178? Your 6 feet 210 there isn't a ski length out there that should intimidate you. You could 190s for park and be fine.