In the first cutscene of spartan ops we see 2 4s talking about how they made the ladies of some city feel safe and secure...
And then 1 of them flirts with Commander Palmer...
So how different are there augmentations compared to 2s and 3s?
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The book that comes with the limited edition has the Spartan (cannot remember his name since I just skimmed through it) mentioning that his augmentations took months, so they put A LOT of them.