i guess it depends what u want to save...
external can be built tuff and will work to a point, on a soft top or single cab you can include the
triangulation braces for the extra rigidity and you are sweet.
A quick search of old threds will reveal plenty of discussions on cage designs and why certain design features are desirable in different situations. The cage exists to protect the occupants, if you are worried about panels they're called brush bars.
http://www.pointnshoot.org/index.php?mo ... ges&fid=21
shows a pic of a sierra that rolled at willowbank on the offroad practice track at pace, other pics showing bar design and proximity to panel work there as well.
The trick is to utilise triangular shapes in the frame design rather than squares, can be done to varying degrees with an exo, but on hardtops some critical hoop bracing is missed unless you puncture the skin of the vehicle.
That being said, you can always create a crash that will defeat a cage somehow and seriously maim or kill the occupant.
Contemplate the driving you will do, your driving style and talk to people who make the cages and use them in anger, then make your decision.
Spock