My thoughts on this are based upon one over riding issue. Cold starts or just initial start up wear. Ya know the beast has been waiting to go out & play and ya jump in & light it up and the oil is cold. The syn oil seems to be better on start up wear protection. I don't know for sure if the evidence is overwhelming on the side of syn oil?
Next is what's going on before the oil gets to it's proper operating temp. To me this is even more important. In most owner's manuals there is a bit about how until the oil comes up to temp don't put too much load on the motor. In our manuals it says to be below 2k rpm's until oil temp is at 140*. This is where syn oils excell. There is overwhelming evidence here that they are just better at lubricating at low oil temps than any dino oil. Also as a bonus they are more stabil at high oil temps so they do a better lube job at that end of the temp scale too.
JMHO
Tom