No contest. 645 very centrally located. It is also center of ship on lowest level of rooms. 703 is exactly same size, but very far forward. Another problem in 703 is that your balcony may be very visible to 701; not positive on this last point.
Go with 645; you won't be disappointed.
"The test of a first rate intelligence is the ability to hold two opposed ideas in the mind at the same time and still retain the ability to function."
F Scott Fitzgerald
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