I ride a liter plus bike, & have tried a few 600 class bikes, but the small bikes are not for me, I like to ride lazily & ride mountains, without screaming through the gears, & routinely ride 2up, & maybe have 500+lbs including luggage, try that on a 600 bike, yes it will haul it, but not relaxed, at low RPM, I normally manage 50+mpg even when doubling across mountains.
my hard fast riding days are over, I have nothing to prove, I have rode many hundreds of thousands of miles in my life, alot on older Harleys, or vintage Kawasakis, Hondas, 70's style bikes. my present ride is a 96 Kawasaki GPZ 1100, a sport touring machine. not been 90mph on it, believe it or not.
in my younger days I used to average 40,XXX + miles a year, now days around 10 to 15,XXX miles on 2 wheels a year, last year I only managed to get 9,XXX, but had a few problems, & no money to fix, & had broke a few ribs & went a couple months without riding.