Canvas has also had some really weird performance issues in the past that are browser specific. Chrome once decided that the number of images used was too many

Canvas has also had some really weird performance issues in the past that are browser specific. Chrome once decided that the number of images used was too many in an animation, so it had to decode some of the images in the animation on the fly. This obviously killed all performance. This bug has been fixed, but I'm sure there are many others like it around.