The carbide tip on these tools are massive advantage to your woodturning. They make for easy starting and remove the need to sharpen. They stay sharp for longer. When you need to you can replace the tip.
The square shank means that you can hold the tool dead flat on the tool rest greatly improving your safety and accuracy.
The square cutter of the rougher is designed for rough shaping and outside curves. There is also an option of a radiused cutter. Radiused square cutters bulge out slightly on the flat sides, this makes them more effective at smoothing cuts.