To be honest you can use either method (including sub'd's) for anything, they are all very versitile toosets in the right hands, for example, I cant use NURBS to save my life (well I probably could but it would take me ages). I pretty much model everything straight in polys, maybe with some sub'd to get the shape etc.
Some people use nurbs primitaves to get he basic shape then go to polys and then to sub'd and then back to polys but that's just one workflow as I go polys pretty much all the way..
As your starting out you are probably best off trying different tutorials, be them from here, a book or free from the web using all the different methods and then determining your own workflow using your knowlage for the situation.
In the end like I said its up to the person to use the various methods that they feel comfey with to get the job done, so theres no hard and fast rules.
"No pressure, no diamonds" Thomas Carlyle