we've been running load tests with both APEX Listener and OHS for some of our applications and couldn't find any noticable difference in performance. Both components can be deployed to multiple nodes for load balancing.
I don't know of any document on that topic, but there are a few blog posts etc. that could be helpful, e. g. [url http://dgielis.blogspot.de/2012/08/moving-to-oracle-apex-listener.html]Moving to the Oracle APEX Listener.
If you don't have a productive environment for your application yet, I'd recommend to consider APEX Listener, as it is under active development and already has some features for current web technologies (e. g. support for RESTful services) OHS doesn't have.
If your current production environment is based on OHS, you should check whether you use some features APEX Listener doesn't offer.