Just because desktop always wins in theory doesn't mean that you can't exceed the performance of existing native clients. I'm sure Illustrator leaves a ton of performance on the table simply by virtue of having a large legacy codebase. For instance, if it becomes practical to assume that all of your clients support GPGPU then Illustrator's existing CPU optimized code instantly goes from being a critical advantage to a heavy burden: they have to maintain that code and write new GPU code that somehow fits with the old code whereas you just have to write the GPGPU code. Witness pixelmator curb-stomping Photoshop in the performance department. Of course, that example is Desktop App vs Desktop App but the principle is the same.