:facepalm well obviously a bigger bike is easier to fuck up, and obviously less forgiving, and obviously you should have more experience beforehand, and obviously easier to spin tires, and obviously easier to get into an "oh fuck" moment, and obviously harder to get yourself out of said "oh fuck" moment safely, and obviously not a beginners bike, and obviously etc etc..
This is all common sense, I don't see how there is still a discussion to be had about it.
But, that said, a factor that can't really be measured and is never talked about: Some people have a natural ability on two wheels, understand how a clutch works and how to safely work it, natural two-wheel balance, natural emergency focus and control, natural realization of what will happen if you go try to be a hooligan and how dangerous these bikes really are... while some people look like super uncomfortable retards learning how to ride, who have never used a clutch before and can't balance worth shit. (I'm speaking from my MSF class, 90% of the people there I would NEVER suggest riding a crotch rocket, but there were a couple that had that natural riding ability who could probably learn just fine as long as their heads are in the right place.)
I started on a brand new GSX-R 750 and don't regret it at all. But two-wheels and fast (manual) cars have been my life, so putting them together was not rocket science for me. It's more than just cc's.
I feel like if you've got to join a forum and ask if you should start on a 600, you're not ready.
But at the end of the day, to each his/her own, there are always going to be dumb fucks on the streets, both in cars and on bikes.
Ride defensive as hell :cheers