There is a big difference between using an object model designed for UIs and using the DOM or canvas, even with the same language (JS). An appropriate model can

There is a big difference between using an object model designed for UIs and using the DOM or canvas, even with the same language (JS). An appropriate model can vastly simplify and accelerate layout and painting. I'm thinking of QML here - the performance situation is probably similar with XUL, ugly as it may be.