So, now the main point of my post... I'd be really interested to hear from anyone with both an E-M5 and E-M1 about differences they've found between the files from the two cameras. I love the files from the M5 and P5 and of course they share the same sensor. From what I've seen on the web, there are differences on the E-M1 but the reviews never go into enough detail.
The em-5 and em-1 have different sensors. The 5 uses Sony, the 1 uses Panasonic, at least that's what I'm told.
I own both cameras, along with the gh3's.
My take is the em-5 produces a prettier file in the fact it's more color receptive and has a prettier texture than the em-1 which to me has more of a smoother, but global color.
The Em-1 is a better camera, not as enduring as the em-5, but has a few more features, slightly larger and easier to use, focus is about the same.
I bought an Em-1 because it allowed standard 43 lenses and has a pc sync. The lenses, I've forgotten about because the focus of 43 lenses wasn't great and since Panasonic has come out with fast 42.5 mm primes and soon a 150mm 2.8 the standard 43 lenses are becoming less needed.
The Em-1 also has a better viewfinder, really amazing viewfinder, but if you add the ev-4 clip on viewfinder to the em-5 you get the same results and the viewfinder goes up and down so you can shoot standard and also low like a waist level finder.
I don't understand the shutter shake people mention with the em-5 because I've never seen it.
Actually last Dec. I really was excited about the Sony A7 and tested it next to my em-5 numerous times.
This image was shot at the Sony store (right before they closed) and honestly the A7 had blur, the em-5 didn't.
This is not an artistic but interesting image as it was a room full of mixed lighting from tungsten to led's bouncing around and the em-5 was really pretty, the sony a7 was very global and kind of warm orange and working both later in Raw Developer I couldn't get the same results.
BTW this is cropped to about 2.3 of a frame
here it is at 1000 iso close to full rez.http://www.russellrutherford.com/stony_store_large.jpg
To be fair both the em-5 and 1 focus very quickly, but neither track focus very well.
To track focus the only way I've made it work is to set it to single, and just touch, then shoot, touch then shoot and for medium speed subjects the em-1 will hit focus.
My bottom line is both cameras are very good, shoot way above their format and both are close to equal to any less than 20mpx dslr made.
The em-5 is really inexpensive now about 1/2 the price of the 1 so with an ev-4 finder you probably have as good if not better camera than the em-1.
In fact the em-5 has more latitude than my 1dx
But before I spent the money, I would rent a em-1 from borrow lens and see for yourself.
I really have to admit that the em-1 is a very, very, very well built camera.