I'm thinking of learning some tutorials on making some small indie game and I was wondering which would be more efficient? The Source Development Kit (Valve Inc. Half-life 2, Team Fortress 2, Portal) or the Unreal Development Kit? (Epic Games, and thousands of other games, includings Gears of War, Army of Two, Unreal Tournament, and Bioshock.) For texturing, mapping, and all the other fun stuff, so which should I pick?