Hippie is right on that. One of the hallmarks of a good pinot grigio is it's almost citric crispness. The tannins in the oak will cover up much of that acidity and give you a smoother, almost buttery taste like in a chardonnay. I would vote for no oak at all.
You can go either way, but my vote is for no oak. If you want some, stay on the light side as too much oak will overpower your wine and you can not take oak out of wine.