The pipe cleaners are a bit stiffer, but they break in more, where as the Walls will pretty much stay where they are (they'll get slighty softer).
They did make the Walls a bit softer this year too.
The walls will be more durable and have a more balanced feel on rails (because they're symmetrical), while the PC is gonna be lighter, faster, and carve better into jumps. Both do very well on groomers too.
I'd say, if you're gonna do more jumps that rails go with the Pipe Cleaner, if you're gonna do more rails than jumps go with the Wall - easiest way to put it.