I also much prefer the Speex version. The robotic noise is consistent and easy to ignore. The NN version has a "choppy" feel to it that catches my attention. It reminds me of H264 vs VP9 video codecs at the same bitrate. VP9 is supposed to be better, but H264 artifacts are more artificial looking. VP9 artifacts look more natural, almost like mold/decay on film, which I find more distracting.

I prefer your hacked RNNoise version to the original, but I still prefer the Speex version. Robotic is predictable, and predictable is good. I don't want denoising artifacts to feel like there's some intelligent agent behind them, just as I don't want any software tool to feel intelligent. The smarter the tool the more jarring it is when it misreads my intentions. It might help average performance but it harms worst-case performance, and worst-case performance is subjectively more important because humans pay attention to outliers.