Thoughts from those using both m43 and Full Frame DSLRs - that certain something?

The first is Aperture/diffraction. Most/many M.4/3 lenses are optimal around F/5.6, with diffraction also kicking in by F8. With the base iso starting at 160, in bright Asian light there's a good chance you were at F8 and beyond, missing the lens sweet spot and suffering some diffraction. A good quality ND filter may have helped.

Next, dynamic range (exposure range). I was very disappointed with my GH2 in Asia, always fighting the bright highlights. I'm much happier with the results I'm getting with my OM-D. There was close to a stop more highlight recovery in the 5D2 over the GH2 which mean't different shooting techniques, but still, nearly all my good GH2 results came from UK shoots or less bright Asian scenes (shade/canopy). Again, perhaps considering filters more would have helped.

Next, light/time of day. This carries on from the DR comment. You said your 5D shots were more likely from longer breaks such as towards the end of day. Obviously the light towards the end of day is more interesting than broad daylight, and nothing impacts the quality of a photo more than the quality of the light.

Shutter shock. The extra bulk of the 5D2 acts as a shock absorber and all but eliminates camera induced motion blur at normal shutter speeds. The lightweight of M.4/3 sometimes acts to its detriment.The 1/FL rule of thumb needs adjusting when you use M.4/3.

The lenses. Despite the current fashion for bashing Canon, they make some exceptionally fine lenses, including that TS-E24mm you have. I have the TS-E90mm and the rendering is like nothing else I've seen. I can easily tell my TS-E shots from a great distance. It's not ideal for every shot, sometimes it's too sharp / contrasty and spoils the scene, other times it makes it.

I love my OM-D and the newer high quality lenses and I'm happy shooting it daily. But I've not abandoned FF.

When I look through my collection, my most stand out images come from my original 5D, which just has a special rendering. The 5D2 added lots of better features and is an all round better camera, but it lost a little something in the rendering over the original. My other stand out images come from the Fuji X100 which I'd still be using if Fuji officially acknowledged the sticky aperture blade issue so I could get it repaired, although 12MP is too small for some uses.

I'm hoping the 6D with a slightly lower pixel count and more advanced sensor may recapture some of the original 5D magic. with the smaller body and lower weight, combined with the new smaller lighter lenses (like the 24-70 F/4L IS or 35mms from Canon and Sigma) I think I'll stick with FF along side M.4/3 rather than go fully M.4/3.

Just some more food for thought.

-Najinsky