*Mass Effect series SPOILERS*
Actually, already in ME1 you learn the story about how the geth split up from the quarians and that quarians went aggressive against the geth first, upon realising they had "awakened." Of course, in ME1 you fight geth throughout the game, so you'd be naturally more inclined to support the quarians...
As someone who romanced Tali (the only halfway decent option so far in the series (Kelly was too much of a side character)), my answer is easily the geth. Because of the aforementioned story, the moral advantage is certainly on their side, and they would be of much bigger use for the future of the universe, anyway (even if we disregarded the reapers altogether).
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If you like Blitzball, try Captain Tsubasa II (in English) for NES!
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