Well... Being a guardian means you are essentially immortal, with "magic" powers and you don't have to sleep, eat, pee, or shit. But your whole life is combat or training for combat. Being a Spartan is more like the military lifestyle you are probably accustomed to. Bad chow, little sleep, missing family, combat and training for combat. But you would be the baddest ass around. I like eating, but sleep is a waste of time. I like having magic powers but my favorite superhero is Batman for a reason. So I dunno. They both have up- and down sides. Based on what I've seen so far it looks like the ladies in the universe of Destiny are just a little bit hotter so that may be a determinant (if Mara Sov came with the deal, then sign me up for the Guardian life).