I don’t think the Sportster is a “beginner’s bike”. In fact, I don’t think any Harley is a beginner’s bike. They’re all too heavy, for one thing. Even the Sportster weighing in the neighborhood of 580 pounds is a pretty hefty bike. A beginner will certainly drop it in situations where they could hold up a Rebel.
The Sportster has the additional level of difficulty in being top-heavy. My chick can pick up a Glide off the kickstand, but she can’t budge an 883. She even finds balancing it a bit scary, because it becomes too heavy to hold up at a much narrower angle.
I think the reason behind the bigger bike/chick’s bike deal is purely because the sporty has the smallest engine in the Harley line. I think people just assume that the smaller engine means its easier to ride. I don’t think that’s true, because I think the weight distribution actually makes the big twins easier to ride and handle, especially at slow speeds, despite being significantly lighter. I don’t have any peer-reviewed evidence to support it, but I also assume that the bigger, heavier tires of the big twins also impart gyroscopic stability at a lower speed than the Sporty’s does.
I just think there are a lot of people who equate size with “manliness”–whatever that is–and see 96 cubic inches, and don’t think any further.