Definitely Aldridge. Before that DLC came out, however, I mainly used Sergeant Davin.
The main reason I used Aldridge when I bought the DLC was because everyone else was using DJ Scully and I didn't care much for the other two. As time passed, however, I started to like how Aldridge fit into the whole atmosphere.
I also like him because I also do metal work and have to wear those big clunky gloves (I wish I could see them in the first person view)