Just saw this thread over on FWH by DexterDay called "MS 460 vs Jred 2171". Likely the link here would be censored so just google it. Videos show the proof in the thread, quoted summary below...
A quad port cylinder is hard to beat with a dual port cylinder, but they are very close, likely the extra displacement on the Stihl is helping compensate for the better flow in the Jred.
It would be interesting to see how a ported 460 compares to a "hybrid" ported 460, so I can make some estimation on how it would compare to the XPW cylinder.