I will put on my nerd hate on also and correct you in saying the smoothness of the radius and bend has everything to do with the bender. Most nice cages are made with a mandrel bender (rotary draw bender). They produce nice smooth bends. A press bender (compression bender) will produce distorted bends that which cause an oval shape to the tubing. This is what you will find in most muffler shops as they are quick and easy to use. I am really liking the looks of this EVO cage in how in blends in nice with the interior. But when I do my cage it will probably be something custom as a good cage should be tied into the frame of the vehicle.
A muffler shop would have a "pipe bender" a press bender is made for bending pipes (you could bend steel tubing but will get shitty work out of it because of the die sets. one is a outside radius and one is inside radius). pipe and tubing are different. if you're using a high quality "tube" bender you will get a nice bend from it (assuming your using the correct die set). I was more referring to the smooth transition from one radius to the next. So were-ever your radius segment ends at the tangent point the new radius starts so for that point to have a smooth transition, you're new radius segment center point needs to be on the same common tangent line as your starting radius. This is if you're connecting 2 radius segments to each other and you repeat for the 3rd radius and so on. on a cage you only have one corner bend (eaither a 90 or a 45 deg.) so there's only one tangent line.
It's kinda hard to explain without drawings diagrams and showing pictures so just take my word for it.
I don't have any experience with bending tubing but i do furniture engineering and I deal with this type of geometry fairly often. I'm pretty sure both of the metal fender companies have a jig they precisely manufactured for making their fenders.
For $649.95 (what RH want's for theirs) I wouldn't even try to build my own cage all the hard-work (engineering and planning) has already been done.