The extended VW warranty you buy and pay for before the car is registered is as comprehensive as the one the car comes with for 3 years.
You can buy a year or 2 at the end of your 3 year warranty will cost more and be less comprehensive. The other aftermarket ones are less comprehensive again.
I paid for the 5 year warranty when I got the R - either because we will keep it at least 4 years and sell privately, or i'll sell it sooner with a lot of warranty to the next owner.