Tubes? What is this, 1995?
The Cushcore has the appeal of saving the rim. However big benefits (and especially over other products like Huck Norris) is:
-Lower air volume as there's a pressure ramp-up similar to tokens/spacers in an air shock. So while you run lower pressure, there's less air volume so as you hit a bump you have a ramp-up effect. Part of why you can go with lower air pressure. Not that you're hitting the rubber against the cushcore, but it doesn't have to hit it.
-Sidewall support.