Widgets let you do what live tiles do, but the difference is really in the discoverability. "Pin to start" is pervasive throughout the WP interface, and live tile functionality is built into the "default" app launcher icons. Pull up the location of my apartment in the navigation app? Oh hey, I can pin it as a tile for one-tap "get directions home"? Sweet! Stuff like that.
On my Evo I never made nearly as much use of widgets because adding them to the start screen was a different process from adding apps to the start screen, and not integrated into the apps themselves in the same way as far as I remember.
The other start screen thing I like about WP is that I hardly ever used the stuff on anything but my main, front-and-central home screen on my Evo. I usually just glanced at the home and then shut it off without swiping left or right to my alternate desktops, unless I wanted to launch an app on one of them. The WP "just swipe down to scroll through all the tiles" idea is really convenient for helping to remember everything you pin there.