I truly believe there’s no such thing as the best tweeter, especially if you limit to material only.
The best tweeter is the one that perfectly integrated to a given speaker and the other drivers. I’ve heard ribbon tweeters that sounded odd (poorly integrated), Sol tweeters that sounded lifeless and metal dome (and inverted dome) that was like ice picks. On the same token, I’ve also heard the complete opposite of all… it comes down to the designer and how that fits your preference.