I don' t know where it falls in skill or teaching target but I strongly prefer the done_testing($n) idiom. The main reason is it lends itself to flexibility and a bit of intention documentation in growing/maintaining tests, for example cases like this–

my %tests = ( case1 => { input => …, output => … },
              case2 => { … } );

subtest "Something" => sub {
    plan skip_all => "Moon is not full" unless …;
    ok 1;
    ok 2;
    done_testing(2);
};

for my $test ( values %tests )
{
    ok $test->{input}, "Have input…";
    is process($test->{input}), $test->{output}, "Process works";
}

done_testing( 1 + 2 * keys %tests );
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