Not too similar cards. Which one do you prefer and why?
I run them both, view Giant Killer as more a removal spell than creature when it comes to evaluation. For aggressive decks you want a critical mass of creatures that can apply pressure before the opponent stabilizes with a 3 or 4 drop and Officer lets you get under while also providing flood insurance in the later game. If I had to go with one I'd probably lean towards Officer because W/x Aggro can always use more 2/1s with upside.