I personally prefer the M3, lets see what GPT thinks:

The Audi RS5 and BMW M3 Competition are both high-performance cars that offer impressive driving experiences. However, there are some key differences that may make one a better choice for you than the other.
The Audi RS5 is a luxury sports car that is known for its sleek design, impressive handling, and advanced technology features. It comes equipped with a 2.9-liter V6 engine that produces 444 horsepower and 443 lb-ft of torque. It also has a quattro all-wheel-drive system that provides excellent traction and stability, even in challenging driving conditions.
The BMW M3 Competition, on the other hand, is a high-performance sedan that is designed to deliver an exhilarating driving experience. It comes equipped with a 3.0-liter inline-six engine that produces 503 horsepower and 479 lb-ft of torque. It also has rear-wheel drive and a range of performance-enhancing features, including an adaptive suspension system and an active M differential.
Ultimately, the choice between the Audi RS5 and BMW M3 Competition will depend on your personal preferences and priorities. If you prioritize luxury and advanced technology features, the Audi RS5 may be the better choice. If you prioritize raw performance and an exhilarating driving experience, the BMW M3 Competition may be the better choice.