ffmpeg concatenation introduces video stutter but does not affect audio
For some reason I think this is avoided when using ffmpeg's concat PROTOCOL (ffmpeg -i "concat:...") rather than its concat DEMUXER (ffmpeg -f concat -i mylist.txt).  Oddly, it's also slightly more convenient since using the demuxer requires me to create the text file with the file names in it while with the protocol I can just specify them on the command line, eg: ffmpeg -i "concat:00001.MTS|00002.MTS|00003.MTS" -c copy output.mts

I'll need to confirm this later, I'm at the wrong computer but something brought the question to my attention so I decided to update it with new information.