It's the standard language one. Speech language will return empty unless it is set. Speech language was added to 4.x so that you could define a different language for the speech instead of using the same language as the text / subtitles.
shorthand example... if game.StandardLanguage:getName() == "English" then
-- do something...
elseif game.StandardLanguage:getName() == "German" then
-- do something else
end
getobject example... if game:getLink(VGameStandardLanguage):getName() == "English" then
-- do something...
elseif game:getLink(VGameStandardLanguage):getName() == "German" then
-- do something else...
end