The ABAP workbench has a set of examples to show you how to make the best coding with regards to performance.
You can reach the examples in SE38 transaction by selecting menu Environment, Examples, Performance Examples. You then reach the performance examples demos screen.
On the left hand side you can choose a topic and double click on it. You then see 2 examples of implementation. By clicking on the Measure Runtime button:
Now the two examples are evaluated at runtime. At the bottom you can see the documentation and explanation on what is best to use.