Awhile back, when I was a younger and more carefree rider, I roadraced the 250cc-410cc class with a slightly modified RD-400. I hung out with folks that ate, slept, lived nothing but motorcycles. We had a long discussion one night on what was the "perfect" sized bike. We weighed the advantages of every bike on the market then, the disadvantages they had and tried to come to the ultimate comprimise of what a streetbike (not a race bike...although many thought this would still be the same thing) should be.
There were many arguements over the engine configuration, inline four, V-4 , twin, etc...but the actual size of the engine had been pretty much agreed upon.
As much fun as the smaller 250-500 cc bikes were to ride, the concept of long distance riding, and "highway freindlyness" proved that bigger was going to be better. We understood that a bike "too big" would of course loose all the advantage we cited for a smaller enginged bike...quick handling, or "flickability"...lower fatigue on both the rider ,and ...the bike itself from hours bombing through twisty roads.
Although it was of course a comprimise, and there still were arguements over the engine lay-out, the concensous of all the riders that night, along with a few factory wrenches , and some well tipped waitressess, was that the "perfect bike" would have an engine that fell in between ............875 to 910 cc's. It would have duel disc brakes up front, one in the rear. Alloy wheels, a large tank, and some wide rubber.
It was felt that a bike any larger would in some aspects just be a waste of space, making the bike just heavier... and that anything smaller would not have the potential for possessing the raw power needed to excite a normal human being.
Now, many many years later, I still in my heart believe this assessment. 900cc's is all the bike engine one should really need. With the technological advantanges present today in engine design , and the advances in suspension and chasis developement, this seems even more true to me. Problem today is not many makers offer bikes in this range, and the trend is bigger is better.
1200cc , 1500 to 2000cc bikes are what sells and folks are lining up for bigger bikes...and bigger cars (the every popular SUV's). Partly a trickle down from the popularity of Harleys...or the image there-of , Big bikes sell and are, "whats happening" in the world of motorcycles in this country.
To some extent, this does make sence. America is big...huge in fact, and to get from one side to the other, there are long , endlessly smooth flat and straight highways you can take to get there. These boring ribbons of cement call out for huge heavy bikes , that can drone for hours in high gear...while their riders try to enjoy what sceenery is offered to them along these routes.
Luckliy there are riders out there not content with taking the easy way out and believe the shortest distance between to points is not a straight line....So bikes with a little less weight, and some "flickability" are called for. If you can imagine melding both of these worlds together, you might see how coming up with a universal comprimise of a 900cc bike makes some sence.
So , again, my vote remains for the 900.