I've not tried the Kia or the VW, but I enjoyed it a lot better than the Leaf and found the interior to be nicer. It may be spartan in how it looks, but a great deal more thought was put into the layout than in the Leaf.
The i3 interior is.. bizarre. Two tablets in a plywood holder? But I guess it can have its own novelty appeal. Still I'd suggest the electric Mercedes over this, if one gravitates towards premium German makers. Just my two cents.