Send all scores or only the best?

For the ACT, I heard many different opinions regarding whether to send only your best score or all of them. Some say sending all of them is alright since colleges only want to see what you are capable of achieving and will consider the highest score. Others say that sending only the best one is better because when narrowing down applicants, colleges may consider the trend of the scores and a decline may make you less favorable than an improvement. Which is correct?