For me the clarity of the Canton Ceramic tweeter is competitive with the Be tweeter of my Focal or the RAAL. The Ultra is not.
The Ultra is either the best or second best aluminium tweeter I have heard (I am thinking of the LS50's tweeter when I say this, but overall, I liked the Ultra more than the LS50 for other reasons).
Before I heard the Canton against my other speakers, the Ultra was my champion in this price range and I recommended it to several people who had a budget of around $1000 (or, ideally $800 since SVS's B-stock is consistently in nice condition).
Once I heard and compared the Canton Vento to my other speakers, it was decidedly better in the top end, having the kind of clarity I had only heard from Be tweeters before!
If you did not notice a clear winner, I suspect that you listened to one, then had a wait before you heard the other. The Ultra is good enough that it will impress me, and if I then had to wait 5 minutes before listening to my Focals, I am not sure I would know the difference! However, after listening to them in an A-B comparison with instant switching, the Ultra does not have the clarity of a Be tweeter like the Canton does!