AWS SQS - use case for "short polling"
While you can benchmark this yourself, benchmark testing has shown that there isn't much of a difference in time between long and short polling when the queue is full.  Additionally, with long polling you always have data coming back unlike short polling.

As for when to use short polling the AWS FAQ covers this:


  For example, if your application uses a single thread to poll multiple queues, switching from short polling to long polling will probably not work, because the single thread will wait for the long-poll timeout on any empty queues, delaying the processing of any queues that might contain messages.


Additionally:


  ..if your application expects an immediate response from a ReceiveMessage call, you might not be able to take advantage of long polling without some modifications to your application.


If you don't want to deal with asynchronous queues and multiple threads handling the queues in your application then short polling may provide an easier development path (although you'll have to deal with empty responses).