Which m4/3 maker should I go with, Panasonic or Olympus?

Yes, there are differences in approaches between the two companies, even though they often use the same sensor and sometimes create cameras that look similar (e.g. GF-3 and E-PM1). 

Panasonic tends to rely on lenses to have image stabilization; they do not include it in most of their bodies. Panasonic tends towards more video capability, especially in a few models such as the GH5/GH5s. Panasonic has the only model with fully swivel LCDs (e.g. GH5/GH5s). Panasonic JPEG rendering has improved in recent models, but still lags state-of-the-art. In the US, Panasonic has been poor at delivering product quickly, and has minimal dealer support.

Olympus uses in-body image stabilization, thus can stabilize any lens. Olympus' video capabilities tend towards automatic and fewer feature choices. Olympus supports off-camera flash for some of their models. Olympus only makes models with a tilt LCD. Olympus JPEGs tend to appeal to users more (more contrast, better color, better noise/sharpening choices).

There really isn't a bad choice between the two, only a lot of small differences. I'm a firm believer that how comfortable you feel with a camera will be a large factor in how good the results you get of it are, thus I strongly encourage you to try both and pick based upon that if there is no single other factor that tilts the choice. The Panasonic GH5 is a larger camera than the Olympus OM-D E-M1m2, for example, while the Panasonic GM1 was smaller than any previous or current Olympus camera. 

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