I currently have a rack and pinion on my Keystone Cougar (piece of junk). The slide was so far out of ajustment when we picked it up that one of the drive gears sheared off and the slide went on an angle into the entertainment center and tore off all the knobs on the DVD player.
We took it back to the dealer under warranty and they replaced the gear and adjusted the slide. Two months later, the gears stripped again and we were stuck in a boondock camp in the mountains and couldn't get the slide back in. I was able to tear everything apart in camp and push the slide back in by hand.
I made the repair myself and learned how to properly adjust the slide. Once I did the work, I never had another problem.
My dad on the other hand had a cable operated slide. He had problems from time to time, but learned how to make adjustments and repairs as needed.
Moral of the story. If the slide is properly installed and adjusted, you'll probably be good with either version. If the manufacturer was like Keystone and did a garbage job with installation, you'll be better off to learn how to adjust and repair slides on your own.