what ever cage you get, just make sure its fitted properly by someone who is good at welding.
I've looked at 6/7 cars with cages lately and I wouldn't want to have a crash in any otf them!!
IIRC the OMP needs quite a bit of work to get it to fit, I've heard the Oreca cage fits better.
I am more then likely going to go for the Oreca race cage.
Afaik OMP have sorted that out iirc toastfrenzy had just fitted one and it is fine.
I've got the omp one in my car, it was a bit of a pain in the arse to fit. the main hoop with the cross was slightly twisted. so we cut the cross out bolted it down in the car and re-welded it. otherwise it went in pretty easy.
the main design fault i can see is the rear feet go through the floor just above the suspension cups. so unless your running ast 's or similar coilover style units getting the bolts in without fouling on the springs is headwork.