Zaphaudio compared a few ribbon tweeters to a dome. Full information here :
http://www.zaphaudio.com/nondomes/
Ribbon tweeters
Aurum Cantus G3Si ($213)
LCY 130 ($199)
Fountek NeoCD2.0 ($118)
Bohlender Graebener Neo3 PDR ($55 w/flange)
Silver Flute YAG20-1 ($40)
Dome tweeter
Vifa D26NC55 ($29)
Findings
Vifa D26NC55 ($29) - This cheap little dome tweeter outperforms everything here except for the B&G Neo3 PDR in the non-linear distortion department. It works well at 2kHz like the B&G, but has ever so slightly higher HD everywhere else. On the other hand, this tweeter beats the Neo3PDR in response smoothness and the resulting smooth CSD. (full results shown in the Tweeter Mishmash)
Summary
None of the three true ribbons have very distinguished performance. They are more similar than different. But if I had to choose one, it would probably be the Fountek NeoCD2.0 because of it's durable ribbon, smooth response and clean top end performance. I'm not sure if I could live with that vertical off axis response, as I occasionally don't like to be locked in to sitting ear height. Generally, these ribbons do not live up to their price and hype. This point is driven home by their comparison to the cheap little Vifa neo dome.
None of the true ribbons, when used one at a time, should be used below 2.5kHz. The higher you cross them, the better you will avoid low end distortion. On the other hand, these are all large flanged tweeters, and as you cross higher, lobing at Fc becomes worse.
I often hear people babble on about the shimmer, sparkle and air of ribbon tweeters. These tests show where these "special effects" are coming from - distortion. Ribbons do have a unique distortion profile that many will find enjoyable with some music. That's OK, and it does not have to relfect badly on your "golden ear" status. However, if accuracy to the original signal is what you are after, one of these ribbons may not be the best solution. Ribbons are certainly not the best solution if you want to build a high-value system. Those building line arrays may want to take a good hard look at one of the longer B&G elements.
The B&G and Silver Flute are both planar designs, but they are also polar opposites. The YAG20 is probably one of the worst performers I've ever seen, while the B&G performs on level with the best domes. It's hard to say what went wrong and what went right in their designs. Folks, we have a winner - The Bohlender Graebener Neo3 PDR.