I know Mariner of the Seas isnt among your choices.. but it will be a new ship to Galveston and the prices are terrific. About $100 less for Mariner than for Magic for a inside cabin. Magic will be just like Dream. I wouldnt pick it just because its a year newer than Dream. .. Id pick Mariner which will be a more beautiful ship... and probably cheaper.
Price them both out for your week, as Im sure they could vary. iv been booked for a while on Mariner over Magic.
... and Im platinum on Carnival, just would not pay extra for Carnival.