I think that is a question that has no value - like asking the question:  which is better for you, eating protein or eating carbohydrates?  well, honestly, you need both. 

The only time that I think the question has value is if/when you are looking to buy land, especially if you are moving to a new location. 

I think the more important question(s) to ask:  what kind of topsoils and subsoils do I have, and what do I need to do to improve them?

As one other poster mentioned, you need to have an easy transition between the topsoil and subsoil for the roots to grow from one into the other, so they really need to interact together.

edit: actually, in greenhouse conditions....... hydroponics would say that you need neither one.    :)