[deadlift] + [bench press] -- grip width
Another post discusses using pauses as a way to increase the stress of a lift without increasing the weight on the bar. Modulating grip width in the deadlift and bench press serves a similar purpose.
The most efficient position for the hands in a deadlift is right outside the shins. Moving them outwards therefore results in a weaker pull. The snatch grip deadlift uses this mechanical disadvantage to build strength for the main movement. The more horizontal back angle places a greater stress on the lats and traps, and the wider grip forces us to pull the bar a longer distance. The starting position is extremely uncomfortable, with the extra hamstring tightness making it much harder to set the back in extension. By training an inefficient pull with an awkward starting position we become more appreciative of the regular deadlift.
In the bench press, the best grip for overall strength development puts the elbows and forearms in a straight vertical line at the bottom of the lift. Competitive powerlifters sometimes take an extremely wide grip in an effort to reduce the distance the bar has to travel down to the chest. Besides being dangerous, purposefully cutting short the range of motion in this way is not useful for general strength training purposes. Moving the hands closer together, though, is. This slightly increases the range of motion, puts significantly less stress on the shoulder joint, and engages the triceps more. Like the snatch grip deadlift, training a longer ROM from a mechanically inferior position makes the main movement easier.