Retrofit and Volley are both android networking Libraries which are developed to perform networking operation in android by writing less code. We can also perform networking operation but doing so will require us to use a separate thread to perform networking operation. volley Library has some great features but when it comes to using a library which can interact with Restful Web services efficiently, i will suggest to use Retrofit because we will not have to convert JSON into our JAVA objects explicitly. Use Volley Library when you have to perform complex task like: (1) Cache Operation (2) Loading Images (3) Request Cancellation and Request Prioritization. Overall , Retrofit is more efficient and fast as compared to Volley.
Retrofit, Volley, Glide, Picasso, Universal Image Loader [Comparison] - Android Advanced Tutorial #8