Ok interesting question, assuming you have asked the audiophiles this as you are building audiophile speakers?
I personally am a fan of dome tweeters especially those manufactured by scanspeak in Denmark
as to which is better out of ribbon and CD then I would say Ribbon as the CD will need to be horn loaded there will be time factors and phasing issues to contend with and this would make the design of an audiophile crossover very difficult if not impossible.
If it is for PA use then it depends what kind of speakers you are designing, if you are building point source then I would go with a good CD and horn combo, if you are building and I'm sorry to say this here a line array then I would go for a ribbon or a planer wave generator BMS make an interesting one www.bluearan.co.uk/index.php?id=BMS4510NDH&browsemode=category
pricey at 200 a time but assuming the specs are correct and I've no reason to doubt BMS they are a bit of kit LOL
other option would be an Air motion transformer www.bluearan.co.uk/index.php?id=BMATPL150H&browsemode=category
this one comes with a good horn but again is serious money
considering the potential gains using these and the fact that you will need a minimum of 8 to make an array then well you can see the problem
if ti as an array you are planning I have some designs for cabinets and rigging however I think you may run into issues with insurance