Gary, I didn't even know they were coming out with engines of the sizes you mentioned. I bought one of my daughters a 50cc scooter when she was 15, and for myself, I've had 250cc, 305cc, 400cc, 650cc, 800cc, and 1200cc. But I guess in addition to engine size, I'd be concerned about the weight. A big, heavy bike like that 1200cc was definitely the best ride, and I never crashed it, but did let it lay over on its side 3 times, and it was just about all I could do to lift it back onto its wheels; figured about another 5 pounds and I'd have needed help. /forums/images/graemlins/laugh.gif So when Honda first came out with one bigger than 1200 (1500cc, wasn't it, with electric reverse?), I think it was 100 pounds heavier than my Aspencade.
Incidentally, when I was a young cop on the streets, and the police department was using Harleys, more than once I've heard a motor jockey call another jockey on the radio to come help him set his bike back up. /forums/images/graemlins/laugh.gif At one time, I had a partner who was 6' 5" and a former motorcycle officer and he told me when you let it fall over in the garage, you had to have help to set it up, but when you let it fall on the street, you're so embarrassed you can grab it, jerk it upright, and take off. /forums/images/graemlins/laugh.gif
And of course, I've seen the method done where you get the engine running, put it in gear laying on its side, then rock it up onto the wheels with the front wheel turned left (if it's on its left side), and when the spinning rear wheel hits the ground, it'll jump right up; don't think I'd ever have the nerve to do it myself though.