Sounds like yours is the original HD model and not the Hero HD or newer Hero2.
The three settings go like this:
First two settings are 720p which is still HD but not 1080. Although some consider 720p to be a 'smoother' image. One setting is 60fps or frames per second and the other is 30fps. You would use the 60fps setting when you will most likely want to watch what you recorded in slow motion. I guess since you are drag racing and only capturing a few seconds this will be best setting. 30fps captures and plays and looks the same as 60fps at regular speed but uses less space on data card and pc. With 30fps you can record longer videos on the data card. The third setting is 960. This will give you a video that captures more of a taller image with not so much side to side view whereas first two settings capture wide angle videos with not as much top and bottom view.
The three settings go like this:
First two settings are 720p which is still HD but not 1080. Although some consider 720p to be a 'smoother' image. One setting is 60fps or frames per second and the other is 30fps. You would use the 60fps setting when you will most likely want to watch what you recorded in slow motion. I guess since you are drag racing and only capturing a few seconds this will be best setting. 30fps captures and plays and looks the same as 60fps at regular speed but uses less space on data card and pc. With 30fps you can record longer videos on the data card. The third setting is 960. This will give you a video that captures more of a taller image with not so much side to side view whereas first two settings capture wide angle videos with not as much top and bottom view.