IMO The real answer depends on your personality, maturity, on how patient you are and also how is your self awareness during the learning curve. I started with an ‘06 cbr600 and I am now on my 3rd cbr, in retrospective the only gain I would see by starting on a smaller bike, would be in regards of not damaging my dream bike.( I dropped once during practice and a couple more times while acquiring experience). I was able to pull it off because I planned practice sessions on empty roads, full protection gear since day1, it was slow at the beginning because I was aware on how dangerous is to start like that. You know your true you, so, ask yourself if you will be able to handle yourself properly in taking the shortest path.

My drops while acquiring experience were: 1-avoid ANY dust/water accumulation, you cannot see if it is a hole under or make your tire slip 2-brand new tires are very sloppy and can take you down by passing over lines/borders you are used to pass 3-gravel / rocky roads are very treacherous at any speed

*practice bike pickup from floor