The beginners bike is a common question and the answers are pretty similar, 600cc etc etc.
I get tossed up on that because I have ridden since I was 14 (40 years) and got my motorcycle license in Alberta at age 14. We were not supposed to have bikes over 100cc until we were 16, but that law was not heavily enforced. So some kids had 175, 250, and even 350cc bikes. Almost all started on 50 ,65,80 or 100cc bikes. A 450 honda (43hp and 410lbs) was a big bike, a 650 BSA (48hp and 430lbs)was a real big bike etc etc, and then the 750 Honda came out at about $1800.00, (68 hp and around 500lbs) and a 305 superhawk (28.5hp 350lbs was a hot rod) RD350 at 36hp and 330lbs. All of the above "bigger bikes" were considered not to be beginners bikes.
Now a beginners bike is 105hp bike weighing what , about 380 to 400 lbs, the GSX650F suzuki is about 70 hp and performs better than a 1977 GS750 or the old 750 Honda and on and on, but you get the picture.
People donot have better reflexes, nor do they drive safer, the roads are more jammed, the cardrivers are much less forgiving and they tailgate insanely in the lower mainland etc etc,.
I am not disagreeing with some 600cc bikes as starter bikes, although I think you should start smaller, but I often wonder how we think a 105hp bike that performs about like a formula one bike used to in now considered a beginners bike.
Just some thoughts required , not trying to DIS people who buy a gixxer 600 for their first bike.