Which is the more standard package, getopt or getopts (with an "s")?

which is the wrong tool. getopts is usually also a builtin:

Since getopts affects the current shell execution environment, it is generally provided as a shell regular built-in.

~ for sh in dash ksh bash zsh; do "$sh" -c 'printf "%s in %s\n" "$(type getopts)" "$0"'; done
getopts is a shell builtin in dash
getopts is a shell builtin in ksh
getopts is a shell builtin in bash
getopts is a shell builtin in zsh

If you're using a shell script, you can safely depend on getopts. There might be other reasons to favour one or the other, but getopts is standard.

See also: Why not use "which"? What to use then?

I too would prefer getopts over getopt for the following reasons:

getopt Cons

1. External utility
2. Cannot handle empty argument string or arguments with embedded whitespace in traditional version

getopts Pros

1. Works in any POSIX shell and is portable
2. Works well with -a -b as well as -ab