[TheSollyLama]

Twins offer a broader range of power than I4's which tend to be peaky and pretty gutless up till that near-redline rush.
Just depends on how you like to ride. I'm not finding myself at 10k rpm all that often, so a motor that makes all it's power above that is largely wasted.

I4's a big because that's what gets raced. In racing, running around at outrageous rpm, making tons of noise, either accelerating hard or engine braking hard, is fine. But it's not optimal for the street.
Twins, IMO, are much better street bikes. What makes an I4 kick a$$ on the track is the same thing that makes it a poor choice for the street. Too peaky, too gutless below that 3k rpm range where they actually make power.

The R6 for example only makes 'crotch rocket' amounts of power above about 10k. That means you have about 3k worth of powerband. All at the extreme end of the curve.
Twins make power over a longer stretch of the rpm range, and over a lower portion of it. Where you are much more likely to be when actually riding on the street.
So yes, the I4's have a distinct advantage at the top end. Now ask yourself how much riding you really do at 10k plus.

 

[TheSollyLama]

Not tired of I4's as much as we have little choice in the matter.

It's a problem with repli-racers. Yes, they're sexy and it's what won on Sunday. But what works on the track ain't what works on the street. It's the downside of the win on sunday, sell on monday mentality. What you end up with is a bike all but unusable in real road conditions. The closer street bikes get to track bikes, the less useful as streetbikes they become.
13,500 worth of rpm sounds like a lot. But many of these bikes barely run below 4k. Almost none have any balls below about 7k-8k. And almost all make their real power in a tiny little powerband near the top.
Read a good article on why the stock classes at the AMA races were lapping BETTER than the full on Superbikes. Because Superbikes are hard to ride, being so incredibly focused.You are 'on the pipe' or you are off it. You have to tap dance on the shifter or ride around waking the dead at high RPM. Basically, the bike is only usable for a tiny amount of it's rev range.

The more we want our bikes to be like ricky racer's trophy winner, the less user friendly, comfortable, and drivable they will become. I think it's a razor line the manufacturers are already walking.