If buying gas is no issue, then the RS3 is better full stop. It looks better, handles better, has better interior, sounds better and is a more engaged driving experience. The only thing it lacks is pure Tesla speed but its hardly slow. Once you put gas/charging into the equation, things get more interesting. The Tesla is fast as hell. It handles pretty well too - like a go cart (suspension sucks however). Everything else is a downgrade including the all important fun to drive factor.
For me, my daily drive consists of many shortish trips around my town. Most trips are 5 to 10 miles. Very little highway. No long trips so no range issues. And all of those miles are nearly free in the Tesla. I'm still having a hard time adjusting to paying $60 a week for gas when I was probably charging my M3P for $15 a week. Now, I will think twice about unnecessary trips whereas in the Tesla it never would. Do I need to drive 45 minutes to the brewery I like to get a 4 pack? In the Tesla, yes. In the Audi, we are probably talking a quarter of a tank so I think twice about a needless 50 miles.
In many ways, the Tesla was the better car for me given my current driving needs. It delivers 80 percent of the experience for less money as well as virtually no maintenance. So I certainly miss those aspects of the car. As I mentioned, cars aren't rational and I don't regret my choice but there are some drawbacks. I'm currently getting around 19 MPG since I'm never on the highway. If you do a lot of highway miles and long trips, the balance shifts in favor of the ICE.
You asked if it is a significant departure for it to be worth it. I think it is, yes. It's hard to describe but you just can't replicate the feel of an ICE sports car in an EV. Sounds cliche I know but it’s true. The M3P is plenty fun to drive but single pedal driving just isn’t the same for those of us raised on manual transmission sporty cars. The reality is we will all be driving EVs in 10 (if not 5) years so if you’re thinking about making one last switch, I say go for it.
Agreed with everything you posted. I also think one of the biggest disappointments with the M3P is that it looks exactly like the RWD that goes 5.8. There is nothing unique to it visually, but that’s every Tesla model which I believe might be intentional by the company.