What's the difference between the Audi A7 Ultra and the Prestige?

I'm comparing these two Audi A7 models, and I can't figure out what sets them apart. Both seem similar, but there must be some key differences that justify the price gap. Could someone explain?

The most significant difference between the A7 Ultra and Prestige is the engine. The Prestige comes with a more powerful 3.0-liter V6 engine, while the Ultra has a 2.0-liter four-cylinder engine. The Prestige also has more advanced technology and features such as adaptive cruise control and a heads-up display.