What engine options are available in the Audi A4 models?

I am confused by the different engine options available in the Audi A4 models. Can someone explain the differences and which one would be the best for daily city driving?

The Audi A4 has three engine options: a four-cylinder 40 TFSI, a four-cylinder 45 TFSI, and a six-cylinder 55 TFSI. The 40 TFSI is the most fuel efficient and is perfect for daily city driving.

For a more powerful driving experience, the 45 TFSI delivers a maximum power output of 201 kW and 354 lb-ft of torque. This engine option is best for those who crave a bit more excitement in their daily commute.