ResponseEntity will give you some added flexibility in defining arbitrary HTTP response headers. See the 4th constructor here:
http://docs.spring.io/spring/docs/3.0.x/api/org/springframework/http/ResponseEntity.html
ResponseEntity(T body, MultiValueMap<String,String> headers, HttpStatus statusCode)
A List of possible HTTP response headers is available here:
http://en.wikipedia.org/wiki/List_of_HTTP_header_fields#Responses
Some commonly-used ones are Status, Content-Type and Cache-Control.
If you don’t need that, using @ResponseBody will be a tiny bit more concise.