I've posted this a few times already, but why not once more 🙂
I had the NEX5N + EVF and used it for M lenses. This worked nicely, only problem was lenses that have deep depth of field. For example a 28mm f2.8 lens. Wide open it was ok to focus with Sonys peaking, but stopped down to f4 it was almost impossible.
I bought a GXR M just because it was offered to me at a good price in and I was curious.
Long story short: I sold the NEX and still have the GXR.
Ergonomics of the GXR are much better. The viewfinder is worse by specs, but it does not exhibit the strong colors and contrasts the Sony OLED has which makes it easier on the eyes (altough I miss the resolution and auto toggle).
The EVF is really the ONLY thing the NEX had over the GXR, and this was not as clear cut as it seems.
Sony = bigger, higher resolution
GXR = easier on the eyes, better with high contrast scenes, better with glasses
but what sold me on the GXR was their mode 2 focus assists. This is not a peaking like sony has, but a high pass filtered image. It works supremely well. Focusing even the 28mm at f4 is easy without zooming in.
second thing that the GXR does better and is important to me: for perfect focus you want to magnify the view sometimes. The NEX does this by pressing a programmable button. Push it, and it magnifies, push it again and it zooms out.
on the GXR it is also tied to the shutter: if you are zoomed in, and you half press the shutter, you see the zoomed out, clear view of the subject. release the shutter, and you are zoomed in again with all the focusin aids you have enabled. awesome for classic focus-recompose technique.