Tweeters

It all comes down to personal preference for the most part. There are several types of tweeters available, conventional dome shaped tweeters are built with different materials that will often influence thier sound. Some higher end manufacturers use berylium or other light rigid materials that will extend the frequency repsonse further than others. On the other spectrum you have the soft dome silk tweeters that sound a little milder. However, what is to one man strident, bright, brittle or harsh can be to someone else the perfect shimmer on the high end.

Other tweeters are horn loaded meaning they have a compression driver (typically a piezo driver) loading the throat of a horn. The typical advantage here is that they are very efficient at converting electrical energy to acoustic output. A lower powered amp can drive them to much louder levels than non horns. Some would argue that these have a warmer sound to them.

Yet another type of tweeter is a ribbon driver which is somewhat similar (at least in theory) to an electrostat. The Electrostatic tweeer sandwiches a very thin film between two plates called stators. These plates are magnetized and allows for a much larger surface area. The benefit with this is that the driver doesn't have to move as much and sounds more effortless.

Here's a quick,easy to understand tutorial on tweeters.There is a wealth of other info on the internet if you want to get into the tecnical aspects.

http://en.wikipedia.org/wiki/Tweeter

Earthquake are you leaning toward a specific speaker;if so
you might want to ask questions about that speaker or specific driver and the electronics you are using.
I think you will get better responses from people who have what you may be considering and this will give you more information to help you get what the speaker or driver can and cannot do

Hahnzie said a compression driver is [typically a piezo driver] this is not true. Compression drivers are not piezo electric. They are domes.

http://www.zaphaudio.com/tweetermishmash/

DIYer Zaph tested a bunch of tweets

That zaphaudio list is interesting. Zaph also did a test of ribbon type tweeters that concluded that they tested relatively poorly. A $29 vifa dome outperformed 4 out of 5 on paper. Cant remember what manufacturer I read recently using two domes to replicate the dispersion pattern without using ribbons.
I have speakers with ribbon type "isodynamic" hivi tweeters and I think the high end sounds very nice. Silk, fabric, metal domes, or ribbon tweeters, I think the crossover and overall design of a speaker has more to do with the sound.
My advise is pay less attention to the type of tweeter, and listen without bias. Your ears will find the speaker a talented designer has made for your tastes.

Zaph link is very miss leading. $29 vifa domes no where near the performance of any ribbon of quality. What zaph is testing for means nothing to sound quality or end result. If you look at Zaph they offer most all loudspeakers with ribbons.

I really don't think you can predict the sound of a speaker based on the type of tweeter used. There are just too many variables in the design. The type of enclosure, the crossover, the placement of the tweeter in the cabinet and other variables make it impossible to know what the speaker will sound like without listening. For example, I've seen many people say that metal-dome tweeters are harsh, but Harbeth uses metal dome tweeters in its HL5s, which could never be called harsh.

Don't get hung up on this. Find a speaker you like and listen to it. Don't worry about the driver types.