This is really up to the customer and their preference in most situations. The exception to the rule is a Cathedral ceiling, where ridge vents are required by Code. But remember when installing ridge vents on roofs with attic space, make sure your gables are closed. If left open, your attic will not have the proper air movement needed to remove the heat and moisture that accompanies it. Creating higher energy bills, more ice damns, and rotten decking, not to mention a Code Violation.