Someone started a thread on this a while back and I dug into it just cuz I was (as usual) looking for a productive way to ride the clock.
I may try to find that thread, but my synopsis was that Ruthenium is a much cheaper metal, but comparable in performance to Iridium in this application. So, plug manufacturers could produce plugs that perform as well (allegedly) and sell at the same (or higher) price but profit more since Ruthenium was cheaper.
On our end, I don't think there would be any perceivable difference in performance. And, at that time, they were still so new that there wasn't any real-world consumer feedback. There was only manufacturer "lab test results" with fancy computer-generated pictures of pretty flame propagation. I looked into the Ruthenium metal itself and found that it was considerably softer than Iridium, which made me question it's length of life.
My personal conclusion was that the Platinum and Iridium plugs we run now have all been proven millions of times to perform well past 100K miles so I have no reason to experiment with a new plug, especially if it costs the same. Even if there was a performance gain to be had, I don't see it being anything we'd feel. IMO, stock for stock, if you feel a difference from a simple plug change, your old plugs weren't up to par in the first place.