I needed the Niro for the particular shape of the interior, but on paper, the Ioniq actually has more capacity. I happen to really like the way the Ioniq looks, and if I didn't need to put bicycles in upright, I never would have considered the Niro. The efficiency difference is best case actually more like 15%, which I think is pretty significant, especially at higher speeds.
You are right about the Kona, not planned for a hybrid version. A Kona EV will be released later this year, but won't hit NA until 2019.
2018 Kia LX HEV Metal Stream with Advanced Tech