You could get the best of both worlds if you got a GWX-5600. They have tide/moon graphs AND are multiband (5 or 6, not sure) They're rare, but really nice.
what are you looking to pay including shipping?....are you in the usa? also are you looking for a gold circular tin or a black smaller hexagon-shaped tin?
they're all the same. the full model name/number is dw-6900nb-7dr. the other names are just shorter versions. there a couple different "nb" models, the number after the "nb" signifies the color. 7 means white for most g-shock labeling.