Isolation Transformer vs. GFCI

Currently my EMC students are refinishing and modernizing old 1930's and 1940's AM radios.  When working in the lab on these radios, each student must power their radios through a portable GFCI and use a thick dry leather glove on their left hand (for right-handed students).  What is the main electrical safety advantage and disadvantage of powering through an isolation transformer instead of a GFIC? What is the purpose of the leather glove on one hand?   Humm . . . good PE sample test question.