This is an email I sent to some friends recently... thought it might be useful to some here:
I've been debating between the NEX-5N and the NEX-7 for a while. I had the chance to borrow an NEX-7 for 24 hours and got to use it a bunch.
Compared to the NEX-5, the 7 has a much faster shutter release (I think it's currently the fastest in the world), a sensor that handles low light significantly better (25% better, measured with a light meter), an amazing EVF, better video recording options, audio-in, and better controls. It also has a weak built in flash, which doesn't really do anything for me.
After using it for a day, I was surprised how little I used the EVF. It is absolutely amazing and would be really nice in sunny settings, but overall the back screen is so good, especially with the angling, that I found it faster to not use the EVF.
I did more research into the NEX-5N, and found that it had every new feature the 7 has except for the flash, audio-in, controls, and EVF.
Interestingly, when shooting with a manual lens, as we do, the controls weren't much of an improvement. When you're manually controlling aperture, you basically only need to adjust ISO and shutter speed. Most of the time we use auto-shutter, which means that ISO would be the only control we'd need. We already have a rear dial for that on the NEX-5 / NEX-5N.
The NEX-5N has an EVF that you can buy separately. It's not as sleek as the NEX-7, but the combined bulk of the 5N + EVF is still less than than the 7. Unlike the 7, it can also be tilted. Considering those two factors, I don't think the NEX-7's EVF has much of an advantage.
The audio-in is a really awesome feature of the NEX-7, one that I wish I could have on the 5N. The only alternative is a Sony mic that attaches to the top of the camera. I have it and it's high quality, but not as good as something like the Zoom H1, which could be used with the 7. In my mind, this is the biggest advantage of the NEX-7.
The NEX-5N has a better sensor than the NEX-7. It's 16.1mp vs 24.3, which I prefer for the smaller file size. It does about 10% better in low light, and delivers low light performance on par or exceeding any full sized APS-C DSLR. Photos at 6400 ISO are usable, and at 1600 there's no noticeable grain.
Both cameras have extremely fast shutters, go down to ISO 100 (which gives us fast lens people the option to go a full stop lower in sun to get narrower DOF), and can shoot at 10FPS (if not the best in the world, it's close). Shooting video on both is improved with full 1920x1080 at both 24p and 60p. Shooting in 60p and then converting to 24p makes AMAZING cinematic slow motion shots.
After using the 7 and doing some research, I think it's a no-brainer to go with the 5N. Because Sony did such a bad job advertising all the awesome things about the camera, people see it as being an NEX-5 with a touchscreen, so it goes pretty cheap. You can get one for $550 on ebay.
Here's a video shot with the 5N:
And here's a good review with sample shots:
Since writing that email I bought a 5N and have been very happy with it. I haven't yet used the more advanced features, but I'll be doing that on a trip a month from now.