I think the best motorcycle to learn on is the 500cc Buell Blast as long as you are under 6' tall. Its light, very well balanced, and handles great. I think the new price is around $4500 but you can find a used one in good shape for around $2100.
It is not so much a question of height per cc, it is seat height versus your leg length. When sitting on the seat, you should be able to have both feet firmly planted on the ground. If you need to lean to either side to reach the ground, the motorcycle is too tall.
I am 6'7" and drive a Victory Kingpin... very comfortable. Drove from AZ to Calgary Canada with zero problems. Back was good, ride was good, handling was good. Check it out... you will be impressed. CM