Though both have at times been used, by far the more common in use
recently--especially in the computerized typesetting world--is the
latter, i.e., baseline-to-baseline measure, e.g., 14pt in your example.
TeX, the Output Specification (aka FOSIs), and DSSSL are among those
that measure "leading" as baseline-to-baseline.
paul
Paul Grosso
VP Research, ArborText, Inc.
and
Chief Technical Officer, SGML Open
Email: paul@arbortext.com