At present, for a new learner, go with Spray. Spray is mature and fast and all
around, "just works". Akka-HTTP is the future of stream based HTTP processing
for Akka, but he current 1.0 release lacks the feature parity or performance of
Spray. That will hopefully change with the 2.0 release.
I've had experience building with both. The more-recent Akka-HTTP version's
High Level API feels like a familiar friend if you came from Spray
applications:
http://doc.akka.io/docs/akka-stream-and-http-experimental/current/scala/http/routing-dsl/index.html
(as it should. It's basically the