Claiming too few withholding allowances on W-4 : big refund?

What would your son do with the extra money he would get from having less taken out of his paycheck? Would he save it, use it for needed things, or would he blow it? If he would blow it, then he's better off getting the bigger refund. If he would handle the extra money wisely then he would be better off with the extra money in his paycheck, just not so much that he does end up owing the IRS.