I run a single piece. Purely because I needed a custom tailshaft and I think single piece is simpler and easier to make. I've had no problems with it.
However I doubt it would be worth changing from a 2piece just to chase lower weight and power losses. You'd have to be pretty close to the pointy end for that to be worth it.
Those prices he gives are damn cheap, but then again, that's Malaysian labour costs for you.
Hen