title: Single vs Observable in Java RX
body: <p>In the new release, reactiveX introduced Single, as a variant of Observable 
  <a href="http://reactivex.io/documentation/single.html" rel="noreferrer">http://reactivex.io/documentation/single.html</a></p>
  
  <p>Which is nice to have since in my current use-case, I have multiple executions, and each of them only returns a single result. So it will make sense if I change from using Observable to Single.</p>
  
  <p>But then as a part of my use-case, for those multiple execution above, I need to concat them into one Observable stream later on (to get results from all above executions). </p>
  
  <p>So now my question is, what is more beneficial in term of performance? </p>
  
  <ol>
  <li>Using Observable for each execution, although I know that the execution will return only 1 result.</li>
  </ol>
  
  <p>or </p>
  
  <ol start="2">
  <li>Using the Single for each execution, and only convert them to Observable when I need to concat the streams later on?</li>
  </ol>
  
  <p>Thank you. </p>