i agree with the replies above that showing the power or not, should be determined by the general perception during the time as well as the motivation.
In the ancient days, Buddha Shakyamuni Himself has used power many times to influence people to take influence them into Dharma. But in this era, most of the time, people do not believe in special powers generally. However, at certain time, special power needs to be shown. But this should only be shown with good motivation. Personally, I have seen many cases when power is shown, the people instantly gain faith in the 3 jewels.