I purchased the original GRIN model for all the reasons that a person would even be interested in this option for dental care. Ethically, I was happy enough with my purchase but found that - as an (at times) whiskery-type of person, the gap between the handle and the brush head would snag my whiskers and pinch. I adjusted, but - still pinches.
NADA fixes all that (so far - 4 weeks in) and feels much more secure at the join. No whisker pinches (again, so far). Despite having now a less-than-useful GRIN handle, I feel that NADA was a worthwhile upgrade that works the way I hoped the GRIN had. The GRIN handle will now become a tiny art installation in the pot of some cactus. It will, of course, outlast the cactus and me both.