-OH IS the principal functional group - you were right about that of course.
But if you are looking for the IUPAC name, find the longest chain (if two chains are equal in length, consider the one containing the most number of substituents and functional group).
Moreover, i don't think we use names like tert-butyl, i-propyl etc. although they are accepted names. You are supposed to use numbers for substituents in the IUPAC nomenclature. I mean like, that gives a nice and good picture of a molecule.