I originally bought the rubber ones, as they are identical to what the PT comes with.
They work fantastic
When I reordered, I purchased both the rubber and silicone.
The only difference I noticed is .. the silicone ones don't have that extra thick edge on the end that you push back up into the atty first.
I haven't tried them yet, as I'm still working on the first package that I had open.
They seem to be a bit softer to squish, but that may be because of that thinner top edge.
Buy a package of both
BTW ... they also sell the little top caps that slides back on the shaft to prevent leakage.
Great observation slots. The LV rubber grommets most resemble the grommets from the original PT1 (actually both types are silicone, different "hardness"). In fact, a bit firmer. Why is this good? The "insulator" is the terminator for the circuit. If it fails to make a firm and stable contact of the wire to the assembly housing…you will short. Perhaps you've had some time to compare both and may have found that silicone has a lot more squirm and slip during use. That's the risk to be paid for ease of insertion and aversion to stinky grommet syndrome.
Really though there's little need to experience either shorts or burns but that's a story I'll have to get back to.
Good luck.