It's interesting. I moved from 50cc on up to 400 cc over a period of years and bikes as a dirt rider. Then as a street rider I moved from 650cc on up to 1100cc, again over a period of years and bikes. My first experience on track was aboard my ZX11 at Keith Code. My second time on-track was learning curves, and I was rolling a race-prepped EX500. Again over a period of years and lots of experimentation, I've found 750cc to be the perfect size for me at the track.
Each time I tried a new dicipline, I started small. Dad broke me in this way on dirt bikes, and I guess I saw the value of it. No one else has chosen my bikes for me since, but I keep following the formula, and it has worked.
It seems to me that any rider will crash any motorcycle that he rides. My current bike is the only one I've ever owned that I haven't tossed down the road or at least dropped, and I'm sure it's only a matter of time. The difference is that by graduating from small to medium to large, at least you're less likely to make a mistake that is catastrophic.
This weekend I used an analogy with a student who spoke limited English. Yes, gestures and sound effects were involved. My student very much understood my point.
"When you first try machine gun, no one in room safe! You practice, all bullets start to hit just one wall. Practice more, all bullets hit target. THEN you get bigger machine gun!"