I back-2-backed an R1 and RSV4 in 2017 when I was thinking about buying one of them. I loved the sound of both but actually the R1 sounded even better, it had a really angry bottom end sound to it. Not really what the thread is about but overall I think I preferred the R1 to ride, it's absolutely super, aside from needing a suspension set-up that doesn't rattle your teeth out (and that's even comparing it to Ducatis).
Mate has an R1M with full Ti race exhaust. It sounds mental. The RSV4 is a sweet sounding machine, but the R1M sounds ace. 1198 with just slash cuts sound best. Once you put full system on the tone changes. I much preferred it when it was just the cans.
Straight four engines with flat cranks produce a torsional vibration effect, which a cross plane crank reduces - hence the Yamaha R1 etc. 90 degree vee twin or vee four engines naturally have minimal torsional vibration in any case, which is one of their advantages.
