Do I need sprayed in foam insulation for my garage?

We want to insulate our already dry-walled garage. We plan on doing a blown in cellulose R44 above the ceiling (in the attic). The concern is...we have no vapor barrier in the garage. Some have said we need to do 2 inches of spray foam insulation, THEN enough cellulose to make it a R44...others have said the spray foam is a waste of money. We do plan on heating the garage in the winter pretty consistently. Any opinions? Thanks!