I’ve used the Spree both back when it was doing the Texas flower Gardens and now in the Dry Tortugas and have said on here a few times that you get more bang for your buck staying on the Spree rather than in a Key’s hotel. It is however not a "luxury" liveaboard, it’s a converted workboat and on trips the women usually grab one of the rooms so they have more privacy. Franks safety briefing is worth the price of admission!
I know nothing about the Blue Iguana.