all that happens on RET is a fork/exec, and some variable expansion.
prefrontal_: maybe, maybe not.
it might be a builtin,it might not.
if it is, then there is no fork/exec involved, and thus is faster.
similar with echo.
which does exist in /bin/echo, but you use the builtin in almost all cases.
(i generally disable bash builtins, since the real commands are more featureful)
and then there is the issue of cache...
multiple instances of `time ls' will show different values, first one being the largest, and subsequent (if executed sequentiually) smaller...