I think Prism is gonna be like Teenage Dream, Part II in that she didn't limit herself to a certain sound, she just made a bunch of great songs. Teenage Dream was not cohesive at all, and I actually love that fact about it. Hoping Prism is the same way.
To be honest, the two songs are kind of a let-down as opposed to "Roar", but I think "Dark Horse" is a little better and I think it will be one of the songs that brings out her darker side that more people want to hear and see. It will give people a better perspective of what's to come on the album than "Walking On Air", which I think she does better on vocally than musically.