Earthboxes are portable, reusable, and allow you to avoid soil-related problems like the three F's: fusarium, flooding, and fire ants. Some people only have concrete jungle in their backyard, or rocks, or hard-pan clay which would take a jackhammer to get into.
I suggest if you have soil that can be amended without too much difficulty into good gardening soil either via open-bottomed raised beds or via Earl's "hole planting method" (digging a 2' x 2' x 2' hole and adding manure, peat, and other goodies to it), just do it.
