They're both transliterations Sia-chan. The correct spelling is in a different alphabet, well, technically not an alphabet but you know what I mean.
While 酒 as it is used in Japanese refers to liquor in general, not sake as we know it, it is certainly the origin of the term, and it is written in hiragana as さけ. Every modern romanization system for Japanese (including Hepburn, Nihon-shiki, Kunrei-shiki, JSL, and probably others) uses
'ke' to romanize the syllabic け, which is also assigned the name 'HIRAGANA LETTER KE' by the Unicode consortium... because, well, because they don't know what a letter is.
Anyway, I'm not sure where 'saki' would have originated if it is indeed used, because not only is it not a valid transliteration, it's also further from the pronunciation than 'ke' is no matter how you look at it. I can forgive use of an 'é' to aid in pronunciation, but 'ki' is just wrong. :v
</linguistic rant of the day>