I've tried both in 7*.
The chi is louder, brighter and more free blowing. The low end is powerful, thick and complex. The upper register is moderately bright, but not thin.
The gaia 3 plays like a powerful good playing link while the chi feels like a link on steroids. Honestly, the gaia 3 wasn't too memorable(as was gaia 2... the first gen is by far my favorite), so it's hard for me to recall the tone. I think the dominant reaction to this piece was that it's an amazing mouthpiece, so don't be discouraged to try one.