Thickness, usually is the primary difference. However, once you get to a certain size, the bars are hollow. So the extra diameter compensates for this. Same stiffness, light weight is my guess as to why.
Some bars have 2-3 holes on the ends, so you can adjust the stiffness for say, street vs track. NM Engineering is a popular sway bar. I think when I had mine swapped out at the Dragon, Way Motor Works installed an hSport adjustable. It made a noticeable difference over stock, and the price was right.
Check out Mach V, Dan sells a few different models and he could tell you the differences, if any.
Good luck! :top: