Select Case vs If ... End if

I am writing a function to create a concordance (list of unique words in a document) which excludes common words and offensive words.

I simply have a long list of If ... End If statements to detemine if the word is common or offensive:, e.g.,

if sWord = "and" then Return True

if sWord = "a" then Return true

etc.

It occurred to me that I read somewhere that Select Case was more efficient because the expression needs to be evaluated only once.  My question is - is that true?

Select Case sWord

    Case "a"

    Case "and"

etc.

Thanks.