Hey frenchy.

""""""Why would you prefer it?"""""

I think the benefit (and why its slower) is it will be performing the tesselation in "real time".... so if you have a large scene and are viewing the entire thing, you will render 500,000 polygons, but if you zoom way in to a very closeup shot, you will be still rendering 500,000 polygons... (that number is just arbitrary to demonstrate the point....)

If you export and obj of 500,000 polygons and then zoom way in, you may only be looking at 200 polygons....