The RAAL tweeters are really nice tweeters. I have looked at them and I have done some design work with the OEM version. To me the OEM version was the only one that really stood out. It was a more robust design that allowed a lower crossover point and still maintained a reasonably good vertical off axis response. I could cross it right at 2kHz (barely).
Here is a pic of the pair I designed using it:
It sounded really good on trailing edges, but to me not quite as great on the first strike of the note. This was especially true with cymbals. The hit of the cymbal just wasn't as sharp, but the trailing edge air was very good. To me they sounded more like other ribbons that I have worked with from Aurum Cantus, but better made and a lot more durable.
The Neo 3 by comparison will play lower and has better attack. And I think it is how it handles the 1.8kHz to 3kHz range that gives it an edge over the ribbon. It does give some things up above that range though.
I have also noted that when you put the Neo in an open baffle application it really becomes a completely different driver. It's more relaxed and natural sounding and has all of the airy space and trailing edge detail of the ribbon. This became real apparent with the custom version used in the Serenity Acoustics Super-7. The transparency is on another level. Best upper ranges I have ever heard from any driver.
So taking all of that into account, I favor the Neo tweeter. Then factor in that I can use the Neo's in open baffle designs and I can't do that at all with the RAAL... Then when you look at the price of the drivers comparably the RAAL really looses out. It is really expensive.
