Assuming you don't care about IE, what's the Pros/Cons for SVG vs Canvas? Canvas seems to be pretty nice from what I've used it for so far...
It is also more likely to get faster in the future, as browsers might implement GPU acceleration for it. I wouldn't hold my breath waiting for GPU acceleration for SVG, since SVG is not as easily mapped to drawing primitives, like Canvas is.
There's also a toggle in Firefox's about:config that turns on hardware acceleration on Windows.
When you animate an SVG image, you update the DOM. The browser then needs to parse the DOM (attributes) again, then clear the screen and draw each element again. This is a lot more work than just mapping the drawing primitives of Canvas to the lower-level GPU functions.
Check this presentation for the two technologies compared in terms of how much work is required for animation: http://www.slideshare.net/madrobby/i-cant-believe-its-not-fl...
I guess it's good to have the choice though - for some things Canvas looks a good choice, for others SVG is better.
So if you want to do an online image editor I'd probably go with canvas. For something that needs multiple objects with their own individual event handling - SVG looks a lot easier to me.