Usually pipe of that size would be bent with a Hydraulic bender. The important part is, as you say, the former and you have to remember that the possible bend radius is determined by the ductility of the material you are bending, combined with it's wall thickness.
It is worth bearing in mind that bends in any pipe are tricky to keep accurate (especially in terms of keeping the ben in the appropriate plane and not finishing up with a 'twisted' bend). You may find that you waste more pipe than you actually get right... (speaking from bitter experience here
Have you considered getting the bends made by a fabrication shop and then welding them yourself to keep the cost down?