In my experience a sway bar will have a positive impact on straightline handline regarding bumps, potholes, etc...anything on the road that causes one wheel to go up or down while the other stays constant (not affected by said bump, hole, etc). The sway bar goes up/down on one side but not on the other. And that causes the bar to flex from the applied torque and that applied torque will pull or push on the other side in a likewise manner. In other words, hit a bump and it pushes one wheel upwards. The sway bar swings up and simultaneously pushes the other wheel up (admittedly not with 100% of the same force, but with not much of it lost). This causes the front end to momentarily assume a more equal posture as both wheels feel the same relative force. Hit a pothole and one wheel goes down but the transmitted force goes against the other wheel simultaneously. Since the force has nowhere to go it actually works to minimize the "drop" in the wheel hitting the pothole by limiting the amount of downward motion. At least this has been my observation.
