I think whichever is the easiest difficulty will be the one I stick with unless I've got someone to play with...I have to do that with Rainbow 6 and Halo. I like the sound of blowing stuff up and shooting through walls - I enjoy causing mass destruction and mayhem
Plus the graphics are quite possibly the best I have seen in a shooty game for a while - the detail is incredible. I'll steal Steve's profile to play online and then no one will ever really know if they are against me or him, so if I truly suck worse than usual, he'll be the one who looks crappy and not me