There are various ways the results from fixed grade papers might vary. Firstly the developer may be a soft- or hard-working one - you might find half a grade difference between developers. A diffusion enlarger will give lower-contrast results than a condenser enlarger. Post-fixer treatment like ferri aka liquid sunshine can be used to add more contrast. Film base colour won't affect graded papers, and if you've got purple dyes left in your films, you aren't fixing or washing them properly.
Galerie is a very nice paper with good deep blacks and responds wonderfully in selenium toner - it turns a warm brown whereas Multigrade turns subtly blue-grey and is more difficult to split-tone than Galerie. Mind you, with a selenium/sulphide split-tone, Multigrade has a nice contrast between cool/warm, whereas Galerie splits warm/warm. Such a shame Ilford doesn't make Galerie with the dead matt surface any more - that's progress I suppose!