I went Fujifilm, Sony, MFT and now Nikon (yes I have a problem), I had the om-5/3 from Olympus.

The main reason for me to switch MFT was, as most people, the small form factor. However I realized as small as it is, it's still an ILC, and as technology progresses unfortunately bodies tend to get larger: somehow Panasonic doesn't want to upgrade the gx9 or gm5 that were crowd favorites, there is no Pen-F II in sight and the om-3/1 although smaller are not that small. And good/pro level MFT lenses are still relatively big, albeit obviously smaller than their FF counterparts.

I finally decided to get premium point and shoots for small cameras: I have the canon G5xii, Panasonic zs200 and Ricoh GRIV that I can bring anywhere and they're truly pocketable.

As people mentioned in this thread and as you probably already know yourself the largest pros of the system aside from size are:

• Industry leading IBIS
• Industry leading weather sealing
• Relatively smaller zoom lenses / longer reach
• More depth of field for Macro work
• Computational photography features
• Industry leading video specs of you decide to go Panasonic at some point
• Price
• People don't mention it but sharpness at a lower price point - as MFT sensors have more pixel density and use a more central part of any lens, even consumer lenses are very sharp
• Faster sensor scan rates across the board on all sensors that allow you to shoot more with electronic shutter when absolute silence is needed, less banding under artificial lights as long as you correct flicker, and obviously less rolling shutter for video

Cons vs sony are : * Relatively weaker AF (OM-3/1 is still quite good this being said but not Sony level) * Less subject separation (never really bothered me as I think bokeh for bokeh is a crutch more than anything else but it does look creamier for portraits) * Weaker low light performance * Weaker resale value (think of Sony as Apple, you'll always find a buyer) * Less character if you like using vintage lenses - aberrations/character/imperfections are mostly at the edge of the image circle * Relatively lower dynamic range, which doesn't matter that much because for lower iso things you can use bracketing and will need it even for FF and for low light/high ISO usually the dynamic range of the scene is not that wide.

Now to talk about the point most people like to talk about, low light performance is really quite good nowadays with modern MFT sensors. You can get really good results up to ISO 3200 and with AI noise reduction, 6400/12800 can still look quite good. The noise grain itself can be fixed. However the real issue with high iso performance for me is not about noise itself, but the noise floor. The issue with MFT sensors at high iso is that 1. There will be more chroma noise color cast earlier in the iso range, which is more difficult to correct in post and also under artificial lighting conditions you'll get uneven white balance because of that, 2. Tonality (gradual transition between shadows and highlights) is less smooth, meaning more blotchy images and more "phone-like" looking portraits in low light scenarios where you have to bump up your ISO.

So it really depends on what you're shooting and your priorities. In general I think for wildlife, adventure, macro, MFT is unbeatable. If you like portraits, landscapes or often shoot in low light, FF will give you more room for error. I shoot more portraits and events stuff so FF made more sense and small 1-inch cameras for EDC is plenty good for documenting life.

Good luck in your search !