Premium. My mom has a 2009 (same engine) and the dealer filled it with regular we took delivery of it. It felt sluggish, I ran the tank dry and filled it up with 93. The ECU adjusted timing (timing relates to the combustion process) and the car felt much, much better after about 25 miles of driving with the 93.
ECUs in modern day cars aren't tuned to just accept one type of gas, if they are it'll only be for premium, which performance oriented cars usually specify. First of all, regular gas is dirtier gas - it'll eventually clog up your valves and hurt your motor's performance. Premium is cleaner gas and detonates better as well, preventing engine knock issues. Also, premium has been found to provide better mileage results, simply because it allows the engine to run more efficiently and combust properly.
Any higher-compression motor, anything above the 9:1 mark should be using premium only, even if the manufacturer says regular is okay. A low compression motor, say, 8:1 can do on regular for its entire duration. Your VW has a compression ratio of 9.5:1 - that's decently high and definitely requires premium. It's also a 2.5L 5-cylinder motor.
Use cheap gas on a higher compression motor, and you'll experience some knocking - you may not hear it, but it'll be there and you'll prematurely wear certain components of the motor. Trust me. You can use regular on occasion, and your ECU will compensate by decreasing ignition timing to prevent as much engine knock as possible, even on a performance car - but it is not advised to do it for prolonged periods of time.