The best way to make MacVim's vim (console, not mvim) the default instead of Mac OS X's vim?

I believe this is what you're looking for:

brew install macvim --with-override-system-vim

This will create vim, vimdiff, etc. symlinks to mvim in /usr/local/bin/vim, and as long as /usr/local/bin is before /usr/bin in your PATH, you'll get the results you're looking for.

Earlier versions of brew used the switch --override-system-vim which was deprecated.

The Vi command line switch works.

alias vim='mvim -v'

You can create an alias in your ~/.bash_profile, just add this line to that file:

alias vim="/Users/user/Applications/MacVim.app/Contents/MacOS/Vim"