I've usually felt Resist Magic possibly more useful, myself. Right now tho' I'm not sure.
My Dark Elf, skilled in light armour, has been wearing the Magehunter's Helmet which is chain and is Resist Magic 11%, nice. He's also been using the Ring of Nihilism, with Resist Magic 13%, also very nice. Both items have taken him a long way. However, he's in a higher armour level now.
He's recently aquired the Ring of Sunfire through the quest, which is Resist Disease 25% + Reflect Spell which fits in nicely with Namiras Ring:Reflect Damage 12% + Reflect Spell 10%.
To progress armour wise he must abandon the chain helmet, and also the Sunfire ring may pip the Ring of Nihilism. What he is effectively ending up with is swapping items of Resist Magic for Reflect Spell. What would you do, stay with what he's been using or use the new stuff? Which brings the question back to do you prefer Resist Magic or Reflect Spell?