Having had both on my CJ7, I'd never go back to metal. I enjoy welding and fabrication. I just don't want to HAVE to do it to keep chasing the rust monster. And besides, the fiberglass clip and tub remind me of when I was a kid and working with modles. Hey, I can do that!
As for strength the glass tub is as strong as the metal. I would however protect the rockers and rear quarter panels unless you like fiberglass cloth and resin.
Were your CJ5 mine... I'd leave the glass tub on. Enjoy the rust free environment. But don't forget our friend CJDave and his remarks on electrical grounds! It's a lesson all glass Jeepers should learn
I'm with Larry on the glass. Your CJ has a T-15 transmission, Dana/Spicer 20 transfer case, Dana 44 rear diff, and Dana 30 front diff. Gears would either be 3.73 or 4.27. All of this assumes that the stock pieces haven't been swapped out.