which is more effective?

Which is more effective in stiffening up a car a cage or sfc? To make things on a more level playing field compare the sfc to a 6 point cage cause that goes the length of the car un like a worthless 4 pointer.

Well, the sub frames would be the most unobtrusive addition to chassis stiffness...and theres no doubt that a properly fabricated and installed cage stiffens everything, but at a cost of having to climb over it to get inside...most chassis builders would agree that the BEST way to tie everything together is to tie a 6 or 8 point cage into the subframe connectors...If you are not NHRA or IHRA required to have a cage and you are a street car I would definitely start with SFCs...if you are required to have a cage then I would still do SFCs first and then tie the cage into it...also be wary of swing out side bars...if they are not made/installed correctly, they will still allow the chassis to move, and while it may save you in a rollover it will do nothing for rigidity on your launch...hope this helps..
--Alan