Forum:Zephyr or Duel-SGX?

I'm currently running a dark squad and i was wondering which unit would be better to use. Zephyr is good because of his Def ignoring BB and his SBB does the same but also boosts the ATTK. But Duel-SGX's CRIT rate boost seems useful as well. Which unit should i focus on leveling? My Zephyr and Duel-GX are both at their 4* stage but both maxed level.

Current squad: 6* Death Idol Kikuri, 6* Hell Keep Alice, 6* Inferno Swords Logan, 6* Wise Mage Elimo, 4* Dark Blade Zephyr