Twist, or a retractable mechanism?

The choice between a Twist pen, and a Retractable pen, is largely personal preference.  They are both Ballpoint Pens, the difference is in how the nib is presented, and concealed.

The Twist pen utilizes what is called a transmission that, when twisted, will make the cartridge move up, and down, within the shaft of the pen.  Turning it clockwise, makes the nib appear, and turning it counterclockwise conceals the nib.

The Retractable Pen, also referred to as a "Click Pen", is controlled by a spring-loaded button at the top of the pen.  Clicking it once causes the nib to appear, while clicking it again, causes it to be concealed.

Clicking it multiple times simply irritates those around you.