But several people felt that
    <test/> meant "this element type is declared as EMPTY, so it can never
    have an end-tag"
    whereas
    <test></test> meant "this element is declared with potential content of
    some kind, but for whatever reason on this occasion it has none".

As an aside here, I wonder if this preference has been influenced at all by the sentence from the Recommendation: "For interoperability [with SGML processors], the empty-element tag should be used, and should only be used, for elements which are declared EMPTY." [1]