I've owned a handful of BMWs (no S54 though) but I'm partial so the sound of the S62 V8. The turbo 6 generations were truly a remarkable change for BMW in terms of power, though.

At the moment, I have a Boxster, and the flat 6 somehow feels smoother than any I6 I've owned. I've done some research and sure enough, the inline 6 is (mathematically) smoother than an inline 6. The only way I can explain the fact that the boxer feels smoother is because it's mounted low and behind me, away from steering components? Whereas in my I6 cars, with the engine in front, you feel it through the front subframe and steering a bit.

Funny. I also have a Boxster. 2014 981 S. I love natural aspiration 6 cylinder cars.

Smoother in what sense? My Boxster is stick so the shifting experience is very different. The flat-6 is a remarkable sound - intoxicating. Especially purely naturally aspirated though I don’t hate the sound of the turbo 3.x variations in various Porsches. BMW ZF is great but it’s not the same.

Otherwise, yes - the handling in Boxster is so different compared to the m340. It just feels like it’s on rails around corners. No body roll. And for me peak way up in RPM means my highway merges are an absolute blast / symphony.

Yeah, mine's the same (2013 981 S 6MT). As you know, they're geared to the moon, and taking a surprising amount of rowing to get the most out of the powerband, so often I'll merge onto the freeway and just be hanging out in 3rd at 70 as I look for my spot in traffic and you don't even know you're not in 6th. Turbine smooth.