The significant difference is that with the OEM setup. If the bearings are not monitored, and seize then the bearing surface becomes the aluminium pin until it fails with catstrophic results. With the Nylatron 66 bushes, the bearing surface is the pin, and because the pin is harder than the Nylatron bush, all the wear is on the bush. That means that if there is wear, it is unlikely to lead to a catastrophic failure.
Those bushes are hard plastic. There is a YouTube video of 'mouthfulloflake' beating hell out of one with a hammer to try and get it to shatter. Clearly his attempts failed.
Ian
http://youtu.be/zgW8rj_pIao