It's hard since there's almost no useful examples of guardian equipment or abilities. There's lore saying that Spartans can run at X mph, lift Y amount of weight and react within Z milliseconds, but the most you have for Guardian capabilities is "a snap of annihilating current" or "power of a collapsing star" which probably can't be taken too literally. There's no proof that Titans are stronger than Spartans and there's also no proof that they're weaker than Spartans.