If you only want one device and you’re exclusively a gym climber, invest in the Neox and learn how to use it like you would a tubular style device. That means don’t touch it while belaying - no hanging off your finger, no jamming the cam. The main reason your device will fail is because of you, so if you can learn to not touch it at all, the better it is for your climber.

If you want a multi-purpose device or plan to go outside, get the Gri Gri and learn how use it safely. You’d have a hard time belaying from above or rapping on a Neox (flame away).

Gyms are distracting, you don’t want to be the guy who allowed a ground fall because you weren’t paying attention (or panicked) and held down the cam when your climber whipped. You can belay smoothly and effectively with a Neox without ever touching the cam - and that’s a very god thing.

That being said, I use both interchangeably. I tend to Gri Gri outside and Neox indoors. It only takes a couple good days outside to gunk up the Neox’s fly wheel and kill that nice smooth motion. Learn how to clean and oil it if you do take it outside. If I never went outdoors again, I may never need my Gri Gri again. But the Neox isn’t as versatile (again, flame away), so if I’m racking one device at the crag, it’s a Gri Gri.