For PA systems, I personally prefer 12" with horns instead of tweeters, over anything else. They give a warm, balanced sound, good midrange, and adequate bass.

10" I think have to much mids, and tweeters doesn't have as good high range as horns.

But the best sounding speakers for PA systems I think is either 12" or 18" hornsubs. Even though they are subs, they do both bass and mid, so with a couple of 12" tops and using dual MONO brigded amps that are powerful enough to drive them, you're all set for great sound!

Doc-Z