This search returns zero results.
Searching in the topbar:
Is different than searching in the question title. Also, you'll notice that "favourite" is underlined in red, so while they are both correct spellings, you get many more results in both search areas if you use the American "favorite", and/or take away the "vs".
A workaround. I, as do others, use the Google search,
site:StackExchange sitename <place search query here>, like this one for example, when the Stack Exchange search gives less-than-useful results.