Micro Four Thirds, when announced was supposed to have a number of advantages over full frame.
Gradually as sensor technology has improved they have finally reached there potential.
There weakness is still focusing, but this is something shared by all mirrorless cameras and the new full frame mirrorless cameras are at the moment even worse then there smaller sensored competitors.
Optical physics is a hard task master. A full frame optically perfect 50mm f/1 lens would be large, heavy, slow and difficult to focus. The cost would be far in excess what 99.9% of photographers would be willing to pay.
The smaller sensor allows for simpler, smaller lens, when combined with mirrorless technology it allows camera bodies to be smaller then some photographers could comfortably hold.
This all leads to a small kit and several lens that can be fitted in a small bag and can comfortably carried all day.
These systems have good depth of field and for street shooters using pre-focus techniques can be a real advantages.
Smaller sensors have a multiplication factor to the lens focal length. Wildlife photographers often need long expensive lens and full frame long lens run into many thousands of pounds.
Some of the faster focusing small sensor cameras like the Nikon Series One with a 2.7 crop factor are becoming more popular for users that need long lens. Fitting a traditional 300mm f/4 lens to this gives you a stunning 800mm f/4 lens at a reasonable cost.
So after yesterday’s full frame good and today’s full frame bad post what is the truth?
Should you go for a micro format or a full frame. DX is the compromise, if you want an SLR there are many options but I have to say as a Nikon user I find some of the lens in the Nikon DX lineup somewhat lacking in some areas. In the Mirrorless department I think Fuji have it with there X range from SLR style cameras to Rangefinder style cameras. They have also proved to be a manufacturer that offers great support even to older out of production models.