"tap to rate" vs "scroll to rate"
There are apps and webapps that implement the "tap to rate" approach (display a number of stars, icons or grades and let the user tap on the desired value) and there are some examples that use the "scroll to rate" (display a scrollable list with the stars, icons or grades and let the user scroll through the options) to collect user feedback.
For example iMDB uses the "scroll to rate" in its mobile iOS app.
One pro that I see is that you can add a description to each rating, and it's all laid out for the user. In the case of the "tap to rate" there is usually no space to show that. Also scrolling is accepted on a touch device. It's natural behavior, and if the UI suggests it, the user doesn't have to think about it.
The "tap to rate" conserves space. However these ratings can be displayed in a pop-up, so it's not necessary to display the whole scroller on the screen.
What is your way of adding rating to your mobile app, webapp? Any other pros/cons, opinions?