but i don't think we're supposed to judge whether one was more important than the other...i mean Davy was in the syllabus for a reason...i didn't study volta, i thought he showed the electrons were transferred between two metals with brine-soaked cardboard as electrolyte...and davy showed through repetition of electrolysis experiments that it was the chemical reactions that were generating a current. I still think Davy needs mentioning, his contribution is still a step forward in the development of ideas.
The markers will expect something from Galvani, Davy and Faraday, since these three are specifically mentioned in the syllabus. IMHO, Volta is just there to connect the ideas of Galvani, and their relevance to Davy's work.
i.e. Volta identified that it was two metals in solution causing the trouble, and then he made the voltaic pile, which Davy used to decompose all his beverages.