ok, the differences are actually more than meets the eye. the pipe bender actually FOLDS the pipe, but because of the way pipe is made, it won't fold, so it curves. the tubing bender draws the tubing through against a curved die and lays the tubing along the die's surface as it goes. pressure is spread out over the length of tubing rather than concentrated in one spot. the other major difference is that pipe sizes are taken from the inside diameter and tubing sizes are taken from the outside diameter, meaning, the dies for bending pipe and tubing will be different sizes, even though they may both have the same size stamped on them. the major difference and reason for using tubing over pipe and DOM tubing over HREW or welded seam tubing (regular tubing) is for strength and flexibility. pipe will not flex, it will snap in the event of a hard roll-over, tubing will either bounce, bend or flex enough to absorb most impacts without breaking, in fact, it will likely tear before it snaps. i don't know about you, but i would not like to be tumbling upside down with a jagged piece of pipe near my head.