There is some overlap of functionality, but I'd say the biggest difference is the way it can group together sets of windows. So if you have a specific arrangement of windows for one task (say, photo editing), and different set for another task (say, email and chat), then you can set up individual pages in Tiles for each task.
When you switch tasks, the windows from the first set minimize, and the windows from the second set restore in their places. When you switch back, the windows swap, and everything is set up like before. It makes it easier to switch gears when you're doing more than one thing at once. It helps compartmentalize by only showing what you need for a specific task, for both shortcuts and running apps, so it's easier to find what you need.
