Guardians have more manoeuvrability, speed and damage output. Spartans can take more hits and can process battle situations faster, so it'd be close, but I do believe that Guardians have the advantage.
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Spartans have more maneuverability, speed, and damage output
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Physically, yes, but Guardians are infused with light. It'd be close, but again I state that I believe that Guardians would win.