I would say interactivity. A spreadsheet for example, you are constantly modifying rows. You want that in memory in the browser, not on a server, where you need

I would say interactivity. A spreadsheet for example, you are constantly modifying rows. You want that in memory in the browser, not on a server, where you need to constantly be making ajax calls. How many micro-interactions do you want --- the more you have, the more likely you want an application rather than a site.