I chose the GZ because it had the largest stock gas tank 3.7 gallons compared to other 250cc bikes.
Simple bike: 1 cylinder, 1 sparkplug, carb. and very little electronics or stuff to fail
Also simple means easier to work on yourself and save time and money taking to a motorcycle shop.
I didn't want any frills that could fail and cost a lot to get fixed.
Ride ergonomics: From listening to Carstuff podcast from Howstuffworks.com, they mentioned on an episode to pick a motorcycle that fits your body. And this website helped me toggle through many different bikes available to me on craigslist.
Great tool
http://cycle-ergo.com
I'm a big guy 6'3'' , 34" length pants and 250 pounds so the GZ turned out to be the most comfortable in my minds eye to ride. I had also rode a similar bike in a motorcycle basic ride course. I didn't want to be leaned forward like sport bikes or the knees bent like that.