I had benchmarked traceur and 6to5 on my project. One thing about the project:
~/work/ed master ~(˘▾˘~) ❯ find . -name "*.js" -type f -not -path "./node_modules/*" -not -path "*/public/*" | xargs cat | wc -l
5651node_modules had excluded from compilation, then exclude it from our wc -l.