Slate is generally easier to use and maintain than glass and generally does not have as high pitch.
Glass has higher pitch and is more work to maintain. Crystal may be even a little higher pitch. Copper is generally higher in pitch than slate and is more work than slate to maintain. Ceramic is a little different than all of them and a little easier to maintain.
IMO, a fellow should probably have a slate, a glass, and a ceramic. For kicks, maybe a copper or an aluminum too. One never knows what he may want to hear on any given day.
You have a number of choices reasonably close to Dublin where you could listen before you buy. You have Supreme in Macon, Chad Hutcheson does glass under the name Dominator in McRae, and Dad's is down in Hazelhurst. Further away is Lonzo's down near Leesburg, and he is winning a bunch of awards these days.
Joseph Vaughan used to make calls in McRae too, but that has changed and I don't understand the situation. Oconee Bait there in Dublin used to carry his calls. (BTW, it's getting time for their end of season sale.) Midwest is now carrying Hutcheson's calls. I've kilt Lauren Co. birds on a Dominator.
Beyond those, you have a bunch of guys here and you have well regarded makers like Russell Lynch of Bud N Betty's.
If you can't figure it out, run down Jeff Shepard and hunt with him.