On one hand, Id always recommend some kind of roll bar because its safer, helps tie the car together (better for handling and weight transfer), and gives you the best structure for mounting harnesses. On the other hand, I realize that it may be the more expensive option. But I havent seen much use of those harness bars, and I cant say I like the design idea.
Its your call on what you want to have in the car and how far you want to go, but if you want to stop down to discuss or see any of the cages going in now, that would be fine.