We had a hotly-debated thread on this subject a long time ago. I actually "came out" with my preference for term Holy Spirit, not only because it etymologically follows the Latin, but because the term "ghost" has picked up in more recent times the strong connotation of referring to a disembodied human soul. You could go back and forth. I prefer the French (Latinate / Romance) in the English language to the barbaric Saxon elements ... LOL. Neither term is inherently good or bad, wrong or right, valid or invalid. Both are valid. If either one had been invalid, the Church would have pronounced on it long ago ... since both terms were in use among Catholics even before Vatican II.
So, for instance, when I pray the Rosary and am not praying in Latin, I always use Holy Spirit, but among Traditional Catholics I always use "Ghost" because, as Matthew points out, it's become this shibboleth, and I don't want to cause scandal. Many Traditional Catholics immediately in their minds label you as "suspect of Modernism" if you ever use the term Holy Spirit.