To be honest, it’s more a matter of what you prefer. Corsair makes fantastic products and I always use them for RAM and cases and the keyboards seems nice. But I don’t like the bottom row and I think their keyboards are rather ugly, the quality is probably just as fantastic as their other stuff though.
The Ducky keyboard feels more solid and screams even more quality, but it still has cheap ABS keycaps, just like the K70. The Ducky board also has media keys, although not so many. The Shine 3,4 and Legend (and probably some of their others) has all the media keys you might need though. Also you’ll probably want to buy a separate wrist rest if you go with the Ducky. I had to get one for my Shine 3 TKL, it’s a bit tall.
I don’t think you’ll be disappointed with any of them, both are great keyboards.