Ok, so here's a curve ball to throw at this thread...
How does Schaeffer's Neutra compare to both?
I use Neutra every now and then, and it seems to really help idle smoothness, and dare I say, provide a little more MPG and/or power.
Schaeffer's products have always exceeded my expectation, and they don't seem to make empty promises thru over-zealous marketing like lots of companies do.