NieHow nan-ren!
I just bought a 2009 XB12Ss a few weeks ago and I love it. It's my first street bike in about 20 years. When I started looking at the Buells, I thought about going for a used bike too, but with the 2010 models coming out, and the 09's still in the showrooms, now's a good time to buy new. The difference in price between a good used one & a new 09' isn't so much right now.
I don't know about the older models, but as far as the new bikes go...
I also thought the 900 might be plenty of bike for me (I'm not looking to race anybody with it anyway), but when I looked at the specs, there's only a few pounds difference in weight, and $$. I think the 1200 is a better overall value. I took one for a ride and found it to be very easy to handle. It feels like it's much lighter than it really is, and it really is light for a 1200 (400 lbs.).
You didn't give your height, but based on your weight I'm assuming your not 6'+ tall, so you should checkout seat heights. If you check the specs you'll see the 900 is actually pretty tall... the same height as the 1200-Ss (long) The 1200-Scg is significantly lower, and might be easier for anyone on their first bike.
This might be sacrilege on this board, but If you really just want a dependable commuter bike, you might want to just go Japanese. That is.. if you dont mind looking like a comic book clone, and you dont mind the constant whining.