I would not buy or reject a boat solely on the basis of cored or solid hull, unless it was balsa core below the waterline - that would be a deal breaker for me.
Next we have to talk about closed cell foam core above or below the waterline. I have built boats both ways. Most cored hulls are cored above the waterline and solid below (I have built a number of boats that way and prefer that approach).
But the most critical and most overlooked question for the builder is this: "how do you protect the core around each penetration?" Most sales people don't even know. Unless the builder is removing core and filling with epoxy or making the area solid FG, the risk is elevated. I have seen 50' foam cored hulls with elevated moisture content down the length of the hull, from a poorly installed chain locker drain at the bow.
On the used boat side, that is where the survey is so critical because even if the builder did it properly, what about the hack who later installed a fitting and simply wiped the core with some sealant?
We all know that every boat has compromises. In my view you have to look at the whole picture and in my case, I would not rule a boat in or out based on whether or not the hull is solid or cored - unless cored below the waterline with balsa Plenty of people can chime in that their balsa is fine after x number of years, and that's good news. But they are the exceptions.