What is the difference between the Audi A8 50 and 55 TFSI engines?

I am considering purchasing an Audi A8, but I am unsure of the differences between the 50 and 55 TFSI engines. Could someone explain the technical specifications and any advantages or disadvantages of each engine?

The Audi A8 50 TFSI engine has a 3.0-liter V6 turbocharged engine with 335 horsepower and the Audi A8 55 TFSI engine has a 4.0-liter V8 turbocharged engine with 453 horsepower. The 55 TFSI engine provides stronger acceleration and more power, but the 50 TFSI engine offers better fuel efficiency.

In terms of fuel efficiency, the Audi A8 50 TFSI engine gets an estimated 23 MPG while the A8 55 TFSI engine gets an estimated 21 MPG. Both engines are paired with an eight-speed automatic transmission and come with all-wheel drive as standard.

If you are primarily looking for speed and power, the Audi A8 55 TFSI engine is the better option. However, if fuel efficiency is a higher priority, then the A8 50 TFSI engine is the way to go.