Apart from the fact that they look sweet in the engine bay, they will give slightly better throttle response as there is no pressure loss. If you try pressing against the standard black silicone pipes you will see how much they can bend...hence expand under high pressure loads.
I had a chat with abbey about this as why should I.
Evryone has commented right so far and I think the main reason is for holding the boost corectly and making sure the flow is right.
As the std pipes are rubber they have been known to collapse as higher boost levels, so as your have the steel turbos and may think of running over 1.2 bar then a wise investment, especially as you move to 1.4 bar and over.
Hope this helps.
Plus they look nice!! (if you are a tart like Paul)
also nice big lips are good to see and very sporting. Mind you no one wants to see it looking like a stuffed kebab or vertical sea food taco or a set of John Wayne's saddle bags.
you get a lot less air loss that way aaaiiiiyyyeee.