planning ahead for the dome home

Hopefully, within the month, I will be on my way of building a geodesic dome home. The one I think I'm going to go with makes it simple. As it uses hubs and all you do is bolt straight cut lumber into the hubs. What I haven't decided on yet, is slab, or deck.
Since this will be in northern Florida, the frost line shouldn't really be an issue.
The dome will be 47ft in diameter. I'm thinking if I go with a deck, I could just simply build a square one that is 55ft. Then I'd have 8ft all way the around built in.
My idea is to level out two feet below ground, and build the deck two feet above ground. Which would create a nice crawl space. For the floor of the home itself, or maybe throughout, use 12" or 16" wood i-joists. with two foot centers. As the only real weight on the inside floor will be dividing walls.
Inside the home for the base of the floor, install plywood. Yes, I know how to build decks as I've done them before. But not to code. I am aware that I will need cement pilon footers every so many feet for the deck.
But what I'd like to know is, which would the cheaper route be? Deck as described or slab with a 6" base?
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