I'd say older metal. I have a few reasons, the chief of which is that I've only heard the cream of the old school, but when it comes to modern metal, I have to plough through so much generic toss to get to the good stuff. I'm sure there's a festering underground ocean of shitty old-school metal that I'm blissfully unaware of, because the Great Magnet ensured it got flushed into obscurity before I even knew what a toilet was. But I have to put up with the similarly rancid turds of today plopping straight out of Apollo's asshole and onto my rapidly jading dinner plate.