It seems like you're doing something akin to a high bar squat. Having a grip as close to your body as possible will allow you to pinch your shoulder blades together tighter and ensure that the bar is resting across the meaty portion of your upper back - the trapezius - rather than on the spine...
Although I may be comparing apples to oranges, consider the squat, where partial reps are heresy due to the knees taking the brunt of the load anywhere above parallel. It is in my opinion (consolidated by Mark Rippetoe's advice) that nothing but a below-parallel squat (the criteria for which is...