Without knowing more about the size of the files, restore requirements, speed requirements, accessibility requirements etc it's difficult to determine if the Iomega drive is the best option.
Looking at them they ain't cheap - in terms of price/Gb they're about twice what an HDD is and vastly more than DVD-R. They're quite quick though - up to 30Mb/s
Blu-Ray isn't great either, the media's cheaper than the Iomega stuff but the drives are expensive still. Speed is only about 9Mb/s so a 25Gb disk is going to take about 45 mins to do.