Quote (filling in a few blanks), "Are 6.5 HLCDs comparable to a traditional PA speaker? Is that the kind of sound I'm going to get?"

A 6.5" HLCD is not in the ballpark with a good open air speaker. A Mackey or Pevey or JBL PA speaker typically has a 12" or 15" woofer to mate with the horn tweeter. The enclosure is the size of a 50 gallon drum and it's bass-reflex. So there is much better balance with a typical horn speaker.
A horn-only voice-only PA speaker? No. It's not near that bad. But it can be far more piercing on the highs.
But to put this into perspective....the horn tweeter used in a 6.5" HLCD is at least 10 dB more sensitive than the 6.5" cone speaker. What kind of difference is 10 dB? The same as 10 TIMES amplifier power, OR, perceived as at least twice as loud. So could they tame that horn a little? Sure. But usually they don't. It's unbridaled and angry. If they wanted balanced sound they wouldn't use a horn. Just about any off-the-shelf conventional 1" dome tweeter will keep up with a 6.5" cone speaker. But the goal is maximum peak output for maximum distance projection. And sound quality totally takes a back seat. Brand really doesn't matter. The train has already left the station a long time ago on 6.5" HLCDs.
Classifieds are full of 6.5" product. Savings is important but it's far more expensive to do it twice.
Those trying to push you in the direction of an 8" tower speaker, by any brand, are just looking out for you.