'stylesheet_directory' vs 'template_directory'

get_bloginfo( 'stylesheet_directory' )

//vs

get_bloginfo( 'template_directory' )

I’m curious if about this. I’ve been using stylesheet_directory instead of template_directory to support child themes. But in a lot of examples on the codex oftentimes this isn’t the case. i.e.

function my_login_logo() { ?>
    <style type="text/css">
        body.login div#login h1 a {
            background-image: url(<?php echo get_bloginfo( 'template_directory' ) ?>/images/site-login-logo.png);
            padding-bottom: 30px;
        }
    </style>
<?php }
add_action( 'login_enqueue_scripts', 'my_login_logo' );

Source: Customizing the Login Form

My question: Is this just a housekeeping thing and there’s just too many examples to work through and optimize? Is there a significant point where using template_directory is preferred? Or finally, is there a performance difference that I’m overlooking between these?