The
Whammy Pedal has the advantage of being able to change notes with the treadle, under your guitar's sound. The PS-5 can't do that, and it's a pretty cool thing, but they do have intelligent
pitch shifting so you don't have to worry so much about what notes you are playing.
Then again, with the whammy, you've got the option to go 'weeeeee!' if you ever feel the need.