I think Ekblad was already an NHL quality player prior to his rookie season and he immediately had a positive impact. It's not often you get a rookie D come in and perform at his level at both ends of the ice even when their ice time and opponents are closely monitored, unlike Ekblads. He was terrific.
It now seems like Ekblad hit NHL ice closer to his full potential than most rookie d-men and didn't enjoy the leaps and bounds in development many others do. He's still a very good player but i think he takes a bit of a knock because he hasn't shown the level of improvement others have which in many cases only brought them even with Ekblad.
I will give Trouba my vote but I honestly don't find it to be a particularly easy decision.