Silver is classic, doesn't show scratches, and looks best in any kind of case. The rose gold looks too feminine and the gold looks gaudy/tacky. The space gray is nice, but dark phones only go well with dark cases (though I tend to not use a case).
I ended up reserving a rose gold 64gb in both sizes at my local store. If I hate the color I will just return it and endure the wait for a space grey one