Spartans and Guardians are both creations of BUNGIE so it wouldnt be a shocker that they both are similarly designed. Therefore they both have a similarly time to kill( a long freaking time ). The thing that is in the guardians favor is the over powered as crap exotics. For example the Vex, Hawkmoon, Thorn, Suros Regime, etc. However, tje spartans have aerial vehicles (Covenant and UNSC) which would demolish the poor guardians. However, the Ghorn would quickly solve this problem.