I agree, the 650cc twin class is enjoying a good bit of attention from the manufacturers right now. Used or new, 650s aren't hard to find and are great bikes for the beginner as well as the intermediate and advanced riders.Well the latest 650 has a friendlier riding position than the sportier 600s, but the FZ6 definitely has a nice upright position too. Any of these bikes are just fine, it just depends on how you like the looks and how much ya wanna spend. The Kawasaki Versys is another excellent all round bike. As long as you find a bike with a suitable riding position for you, I just can't see how you could go wrong. Lota great bikes to choose from!
But Steve-o, think about it like the turbo SS vs the 2.4L SS. The 2.4L is b***** but has less power (more of a focus on torque). The 2.0L turbo is smaller but it was designed for significantly higher performance. The 2.0L is more powerful, but for a 16 year old's first car the 2.4L SS would be safer and still feel pretty fast.