Second storey addition cost vrs main floor addition

Looking at a 1300 sf bungalow for a client. The great debate is the rough difference in cost to tear off the roof and add a second storey or to add main floor additions with full basements to the existing bungalow.
Both designs will include renovations to the existing main floor layout, so that is a wash in terms of the cost.
So, is adding a second storey cheaper or the same as addind main floor additions?