Answer 1

with canvas you can draw pixel by pixel.
a canvas is 1 Dom element.
canvas drawings are not realy scaleable.
it is good for complex drawings or even usable with opengl for 3d content.

svg is vector graphics.
it is scaleable and every 'element' is a dom element so it is not that efficient for bigger drawings but good for simple icons, loaders, logos, ect.

Edit: they explaine it better i think haha

http://www.htmlgoodies.com/html5/other/html5-canvas-vs.-svg-choose-the-best-tool-for-the-job.html