preferred video settings
If I'm not overlooking something, the Nex-5N doesn't support 1920x1080 resolution in MP4, otherwise, I'd probably shoot MP4 for convenience.
Since I like to pull stills out of the footage sometimes, I don't want to go to a lower resolution than 1980x1080, so I keep shooting in AVCHD, even though its so far turning out to be an annoying format to work with.
Sony's Software doesn't even pull the clip info off the camera, which is needed for editing AVCHD format video. Its conversion options are poor too, (incapable of 1920x1080 MP4 conversion), and the upload (public sharing) function is miserably poor, hanging up on the slightest connection issue, and will revert to zero, even after uploading 8 individual pictures from a batch of 30, after aborting, zero pictures were on Flickr.
Anyway, the excellent and free XMedia Recode will convert your AVCHD files to MP4 at any bitrate / quality level you choose.
There's also the free VSO AVCHD editor, but calling it editor is a bit off, as it can only render your AVCHD files into blueray compliant video etc, but no editing is actually possible, no cutting, no cropping, nothing whatever.
I have yet to find anything lightweight to cut AVCHD files.
Don't want to load some bloatware like Premiere on my portable just to cut the refuse off my clips.