sam plays way better than raiden. shorter parries, taunts, charged heavy attacks, better ass and he can sheathe/unsheathe his katana with R3 (which i don't think raiden could do).
the levels and bosses are harder but enjoyable, excluding the final boss, which can be a bit luck based sometimes as you might not be able to consistently evade all his attacks.
unfortunately, it's a very short expansion and didn't thoroughly explore sam's character. it's still enjoyable for what it is and worth picking up if you beat main game and thirst for more content.