A wider grip takes a deal of the stress off of the biceps and shoulders. The heavier I go...the closer I bring my grip. I try to go as close as possible on my heavy sets. The closer grip keeps the lats tucked, chest up, back and torso tighter, and you should be moving more weight easier.
Remember that "close" for me is probably a lot different than "close" for most people. Getting my hands TO the power rings on a bar is near impossible unless I've done LOTS of stretching and I squat HIGH BAR. I normally squat with an 8' long bar which is great when you have extreme arthritis in your shoulders.