There are many sites on the web about that topic, what is best, the new and brilliant canvas element of HTML5 or the new redefined ActionScript3? Well, here you can test it on the broswer you want, and in your own computer. Those simple demonstrations only instantiates balls continuously, but is a good way to see the fps drop as more balls appears. Note that the code is almost the same for each one, except for the small peculiarities of each language.
ActionScript3 (Flash) Version:
HTML5 (Canvas) Version:
