Which one do you prefer and why? I personally prefer WASD because it's closer to the other keys which makes it easier to play the game (unless you have three hands).
i use arrow keys for racing games so that my fingers dont slip off the keys, and also because spacebar is used in racing games. for any games that also need the mouse however, i use the wasd keys.
I almost always go with the wsad keys because I've used that setup for years so I know where everything is in relation to them already, only time I use the arrow keys is when I'm playing a two player game on one keyboard.