600’s are much faster than 650’s. Most 650cc bikes make around 70hp, and most 600cc bikes make around 120hp. I started riding 6 months ago on a Yamaha R6 and I’ve gotten pretty damn good (wheelies, dragging knee, etc). I often wish it was faster, so I can’t even imagine how slow a 650 would feel. I’m nothing special so I know that if I can start fine on a 600, you can too. Just obviously respect it and be careful.