There is a definate difference is some of our snakes form when I'm holding them to when my husband is. Some are calmer with me, some seem to 'prefer' him.
I think it has to do with body heat, the subtlties in how we move when we hold them, confidence, and without a doubt ARM HAIR. My snakes have no problems roaming my arms, but some of them really seem to hate my husband's arm hair!