Update: Update, after extensive testing of both. back to the OE 6.01 build that Chewitt released. By far more stable and MUCH better playback via chd. Uses less ram etc. Heck, even samba is faster with sustained 11.5 transfer rates via ethernet vs. osmc at about 7.4 on same setup.
The big downside of course is the lack of addon compatibility for Isengard vs. Jarvis, but for pure video decoding performance there is *no* comparison. OE 6.01 Isengard courtesy of chewitt wins hands down.
Just thought i'd save others the days of testing trying the other before going back.
Adddons will only continue to be a problem due to incompatibility with Isengard but life is full of tradeoffs.
Thanks again chewitt, you really built a lean setup performance wise.