If you are considering one of these cameras, you ought to read this review posted on PhotoClubAlpha. It is a great and somewhat surprising look at the issues of the larger megapixel count and all the peripheral equipment available (or not) for both.
When I have been editing NEX-7 images at their native 24 megapixels the NEX-5n upscaled image has sometimes looked better overall, and the native size NEX-5n image nearly always wins. The NEX-7 image misses the mark for me maybe 30% of the time.
I really do love the 5N and here is my review from a couple months back.