John, I'm going to guess "both." Your OEM units might be original, and are probably worn out. But diesels do tend to vibrate a lot more than gasoline engines, so I'd think pretty long before I went to a hard-mount or even a poly solution. You might consider replacing them with new versions of the same parts as well.
Isolating the engine from the chassis will make for a much-improved daily ride and drive experience, but at the expense of some rubber wear parts. Some manufacturers are even using oil-filled isolators these days... My FFR Roadster has the V12 hard-bolted direct to the chassis engine mounts, but I wouldn't even consider that (or anything close) for the G3F. Just my $.02, no charge!
FFR1004105RD - world's first twin-turbo BMW V12-powered FFR Roadster
2011 Dodge 2500 Cummins 6.7L - biodiesel-fueled daily driver
JHETTO: 2001 VW Jetta TDI, intended as G3F donor, FOR SALE