Alright, I'm gonna put it bluntly and use small words.
Pipe benders are for PIPE! If you want to get a bender in case you "want to do a rollcage" then you will need a TUBING bender. Pipe is for transporting fluids such as propane, air, water, gasoline, sewage, etc. It is not to be used for structural members.
I don't want to hear arguments about what kinds of pipe have what mechanical properties and material specs. Most people who pick up that shitty HF bender are driving straight to the hardware store and getting a truckload of good old black pipe. Building a proper rollcage is going to cost money. You're either going to have to pay someone to build it for you, or you're going to have to bite the bullet and buy a proper bender. There is no substitute for a properly design rollcage built with the proper materials.
You want to use black pipe for sliders or a bumper? Fine, it's not going to kill you (or anyone else) when it collapses. And none of the benders listed here will do exhaust work. Very thin wall tubing requires yet another bender. The HF, JD2, and Pro-Tools benders will kink thin walled pipe and tube.