Amount of time required to install an icon editor program < Finding a web based icon editor application*

[Ignoring the actual time needed to use the application and create the icon. I can guess that a native application will further reduce this time.]

* As I wrote earlier, because of browser limitations, there are very few web applications geared towards icon editing/image editing.

Off the top of my head:

- You generally own the license to the installed software in perpetuity. Your application source art will always be readable.

- It will integrate better with your desktop user experience. Printing, drag-and-drop, copy/paste of complex data, input devices (wacom tablets), etc.