If you are having trouble with your grip chalk will certainly help, but you could also try out a hook grip as well. Oly lifters use this, and although it is awkward at first just stick with it.
All you do is grip the bar like usual, but instead of wrapping the thunb over the knuckles you position your thumb underneath the fingers so that you are essentialy gripping your thumb as well as the bar. Sorry if that is confusing, but its kinda hard to express it in words. Anyway it is usually utilized with an overhand grip on the bar, but I think it may also be used with an over/under grip?
Anyway, to answer the original question, it really depends on what is more comfortable to the individual. I would try both styles, along with varying widths with your stance and your grip location on the bar until you find what works for you.