All probemaster cables are silicone insulated. The soft grips of their probes are PVC, though.
The 8000 series have the probe permanently affixed to the lead; the 9000 series have detachable probes.
The 8000 series accessories screw onto the probe, over the tip. The 9000 series accessories plug into the leads after the probe is detached. One advantage of that is the ability to use other manufacturer's 4mm banana jack accessories, if you had those.
I think they are both safe enough, the plug-in connection of the 9000 should be as secure as the screw-in connection of the 8000. Having the probe and leads separate gives you a little more flexibility to replace worn out parts, but at a slightly higher price point.