Volcanic Vacation Advice?

I want to take a vacation somewhere that has ample volcanoes. The thrill of climbing up to the rim and peering into the lake of fire is unparalleled, but funds are not unlimited so I can only take one such vacation this year. I'm thinking either Hawaii, with its beautiful weather and majestic peaks such as Mauna Loa, or Iceland, which has tons of volcanoes and plenty of fascinating Viking history which could be explored while resting my legs. Coming from JFK airport in New York, both would be long but worthwhile flights, with the warmer Hawaii taking slightly longer to get to. Which would you recommend, Hawaii or Iceland? Also, what airline do you think is best to take to get there?