I'm interested in making a game using html and javascript. I was wondering if it really is that much faster drawing in html5 and javascript than it is with images and div's in html and javascript.
Example of a game using html and javascript that works nicely: http://scrabb.ly/
Example of a game using html5 and javascript that works nicely: http://htmlchess.sourceforge.net/demo/example.html
Neither of those games requires HTML 5. scrabb.ly does everything with rectangular objects, which divs handle just fine, and the chess game doesn't even use animation. If that's the kind of game you're thinking of building, then what you use should be decided on the grounds of familiarity and compatibility rather than performance.
Fast as in faster rendering or faster development? I would say the answer to both is HTML5 canvas. Although it is a fairly new technology, and not even supported by all mainstream browsers yet, it already has much more functionality than you would have using DIVs with normal HTML. I've done drawing with divs before and it was incredibly frustrating just getting something to work. With canvas you already have a framework in place to do most basic drawing. Furthermore, html5 is new. Even if it is relatively slower than drawing with divs right now (which it probably isn't), that performance will increase as development and adoption increases. I can't say the same for drawing with divs.
Pros to using HTML5 Canvas:
I've run a bunch of numbers on HTML-made drawing versus Canvas-made drawing. I could make a huge post about the benefits of each, but I will give some of the relevant results of my tests to consider for your specific application:
I made Canvas and HTML test pages, both had movable "nodes." Canvas nodes were objects I created and kept track of in Javascript. HTML nodes were s, though they could be or too.
I added 100,000 nodes to each of my two tests. They performed quite differently:
The HTML test tab took forever to load (timed at slightly under 5 minutes, chrome asked to kill the page the first time). Chrome's task manager says that tab is taking up 168MB. It takes up 12-13% CPU time when I am looking at it, 0% when I am not looking.
The Canvas tab loaded in one second and takes up 30MB. It also takes up 13% of CPU time all of the time, regardless of whether or not one is looking at it.
Dragging on the HTML page is smoother, which I suppose is expected, since the current setup is to redraw EVERYTHING every 30 milliseconds in the Canvas test. There are plenty of optimizations to be had for Canvas for this. (canvas invalidation being the easiest, also clipping regions, selective redrawing, etc.. just depends on how much you feel like implementing)
Video on the HTML page, while I am not moving objects, is actually perfectly smooth.
On canvas the video is always slow, since I am redrawing constantly because I turned off my drawing canvas invalidation. There is of course plenty of room for improvement.
Drawing/loading alone is far faster in Canvas and has far more room for optimizations, too (ie, excluding things that are off-screen is very easy).