FFmpeg word concat

Not working:
ffmpeg -f concat -safe 0 -i <(printf "file '/Users/peter/Desktop/WordHeadingsWo.mp4'\nfile '/Users/peter/Desktop/WordClipsWo.mp4'\n") -c copy "WordsWoFailed.mp4"

Working, but slow:
ffmpeg -i "WordHeadingsWo.mp4" -i "WordClipsWo.mp4" -v debug -strict -2 -filter_complex "[0:v] [0:a:0] [1:v] [1:a:0] concat=n=2:v=1:a=1 [v] [a]" -map "[v]" -map "[a]" "WordsWo.mp4"