Hmmm...I think this is actually a complicated question, balancing weight/power/torque with a particular use case, rather than "size" per se.
Here in the Southwest, there is quite a bit of "straight, flat, boring and fast" before you get to the twisty bits. That's a different use case than if you live where there are only twisties, or whee everything is "close."
Making it even more complicated, I've come to the conclusion that top shelf suspension is more important/more rewarding than more power. You use good suspension every mm of every ride, which is quite unlike that additional 10 hp.
Thirdly, on the street, for me, low and mid range torque outweighs top end power b/c the low/mid range is where you spend the vast majority of your time. Especially if you like to "roll and go" rather than bang multiple downshifts every time you want to pass.
Finally, "cadence" matters a great deal to me...especially on a travel bike. I want something that "feels" relaxed if I'm going to spend all day, multiple days, on it.
As some of you have probably already read, I've personally settled on the 450 lb/100 hp/60 ft lbs as the "sweet spot" for me. The "enough" bike, that does most everything I need. And I've also settled on twins as my preferred engine design b/c of the low and mid range torque (generally) and the relaxed cadence (again, generally).
I'm very glad to see some manufacturers bring top end suspension to the middleweight class. I hope they start focusing on weight reduction as well. The BMW F900XR is a good example of a "missed opportunity" IMO...steel frame, double sided swing arm, 13 lbs heavier than the bike it replaced.
And belt drive...I have to throw that in. Simply the best street bike drive system available when designed properly. Zero maintenance, easy to replace, lasts longer than any chain. Did I mention ZERO maintenance?