We've selected SVG over Canvas for many reasons.

I'll try to elaborate a few:

- With SVG we can easily draw very complex geometry, resulting in nice looking, configurable stencils, interactivity and many other features that would've required immense engineering efforts to achieve in pure Canvas backed up by heavy Javascript. This would've have reduced our creativity and ability to adapt fast moving forward. Creating new stencils and adapting to new UI trends is a breeze now. With Canvas, the situation would've been different and highly coupled in the back of the Javascript code.

- SVG is resolution independent. While we haven't optimized Moqups for a full mobile experience YET, if you look at some mockups on any Hi-DPI (Retina) display, the experience is simply gorgeous. Printing is also a great addition, because you can virtually print huge sheets without loss of quality, making face to face collaboration great.

- SVG is heavily used for precise visualizations and technical drawing in industrial engineering, outside its web roots. Not sure how to properly explain this - We just kind of wanted to pay some homage to these folks.

The learning curve for SVG was tremendous though, with many obstacles that made us cringe and almost and  quit at points. This is mostly because SVG is such an underused technology nowadays and the documentation is still scarce. However, it was extremely fun and it's nice to see that SVG is becoming more and more relevant nowadays in the context of HTML5.

About performance: Despite the many optimizations we have done, we still have quite a few technical debts that, once fixed, will make Moqups even faster and behave well with a lot of objects. Beside this, Chrome and others are about to introduce hardware acceleration for the SVG layers soon, so all in all, more good news.

Canvas is definitely faster than SVG for scaling objects in the HTML dom. I had to switch to canvas for the same reason for mockuptiger