Although I've never kept a bare bottom tank, I do like the minimalist and clean, sterile look of it. However, with a ray, I can't see keeping it in anything other than sand. Not for aesthetics, but purely for watching and maintaining the natural defensive burying instincts. It's like taking a fish that prefers cover and putting him in a tank without cover. Sure, the fish may adapt, but do you want a fish with adapted instincts or instincts found in the fish in the wild? I think if you were to provide the ray with conditions closest to it's natural habitat, the lifespan would increase solely on being less stressed living a more 'natural' life...IMO.
I've never had sand either, but read a thread not too long ago about keeping sand out of the filter. A few people in the thread mentioned using sponge covers over their intakes that were lower to the tank's bottom. Hope this helps some. Good luck.