First, turbos are reliable as long as you maintain the vehicle correctly (this applies to diesels also). And, there is no relationship between these 2 engines and vehicle safety. Safety is related to the driver and the vehicle design.
A turbo-charged 4 kind of gives you the best of both worlds: good gas mileage when you are gentle and good acceleration when you need it. If you are looking at gas mileage, a turbo 4 will do better than just about any v6 when driven conservatively. A good 6 cyl engine will generate more horsepower, but not necessarily much higher torque at low rpms (for example, the VW 2L turbo gas engine develops 207 lbft from 1800 - 5000 rpm while the 3.6L v6 generates 280 lbft, but at 2800 rpm). Remember that the larger 6 also adds weight to the vehicle.
VW RECOMMENDS premium for maximum performance, and the engines will run fine off 87 octane fuel. So, it’s not true that you HAVE to use premium or risk damaging the engines.
One other thing to note is that normally aspirated engines are more sensitive to altitude. So, if you live in Colorado, for example, you won’t get as much of the rated torque (and therefore horsepower) out of the 6 as you would out of the turbo 4.