Slant Six 170 vs. 225

More money, more weight, zero gain over a larger dia free flowing single, in the rpm range of a street driver.
Also, from my understanding, better scavenging. You’re only getting an exhaust pulse every 120° of rotation, so its not like 2 Cyl worth of spent gas is fighting for the same space. (Yes of course the same is true for 8cyl)
Plus IMO, tru full duals on pretty much any 6 (at least any I’ve heard) sounds like pure ***. And Im not hatin, I like me some in-line 6s, I’ve owned a few slants, Fords, & Jeep 4.0s. There’s also reasons BMW kept at it for so long.