Click on Wait until or If and wait for the counter to stop after 20 seconds (was 1 minute prior to update to Scratch 3). Note the result and try the other option. Comment below on your results. If you run one test and tehn the other the prev-counter will store the result of the first test so you don't have to make a note of it.
This is in response to a forum query - which is more efficient forever/if or forever/wait until (or just wait until if something only has to happen once). The value of the counter variable is how many times the main loop completes in 20 seconds.
