[aidos]

You sure that's not because of memory swapping? Once warmed up the awk command is much faster for me.

Also, the results are different - though I'm too lazy to figure out why right now :)

[cynwoody]

You need to filter out directory entries.

    find -type f -ls|awk '{s += $7} END {print s}'
    find -type f -print0 | xargs -0 wc -c | tail -1
    find -type f -exec wc -c {} + | tail -1