Coring is a good thing as it adds stability to the cue but the downside is that it changes the way the wood reacts to striking the ball.
Two identical cues made from the same wood but with one cored will hit and feel differently.
Good, well seasoned wood should not warp under normal conditions and I think that most pool cues being made by production makers
(McDermott, Viking, Meucci, Lacusi, Pachauer, Schmelke, and such) are NOT cored forearms or handles.
Using a soft wood that has exceptional looks but is weak would be one case where coring would be needed to add strength.
It takes special drills and extra time to do coring and that relates to a higher price on the finished product.
Personally, all else being equal, I would prefer a custom cue that WAS cored over one that was not just for the extra stability alone.
I made a few cue forearms from Plexiglass and they had a fantastically solid hit and feel but were fragile at the "A" and Butt joints.
I have often thought of coring a forearm with Plexiglass to get that feel but with the strength of wood. Its on my list of things to do.
