el cheapo said:
So a sway bar mounts to the chassis, And its job is to prevent body roll.
Right?
sorry for laughing at you.
body roll is affected by the suspension that is under it, not by bolting things to the chassis itself to keep it from flexing. a STB maintains the integrity of the chassis and the front sway bar reduces understeer/increases oversteer and does lessen body roll, but they are so neccessary, people don't usually refer to them as 'lessening body roll' as 'if you turned going more then 15mph you'd lose control and die'.

for almost all street apps your rear sway needs to be thicker than the front. otherwise you get mad oversteer and that's almost as bad as not being able to turn as you'd like (understeer). subframe connectors maintain integrity of the chassis by, well, what the name says.