Updated: Jun 23, 2020
A ballpoint refill type pen uses an oil based paste ink that is deposited to the page as the ball rolls it out. Ballpoint ink is smudge free and ideal for left handed writers who fret over getting ink residue on their hand as it passes over the line of text they've just written. Ballpoint refills are generally very efficient suppliers of ink, allowing far more writing to be done before the ink runs out as opposed to rollerball refills. Ballpoints are able to write on most any surface and paper, including coated papers. They are also ideally suited for applications requiring extra pressure, such as two- and three-part forms. Ballpoint refills from the Fisher Space Pen company can also write upside down, on vertical surfaces, and in extreme heat and cold.
Rollerball ink (both traditional rollerball and gel style ink) is a more liquid ink that deposits a darker, more fountain pen-like inky line on paper. Like fountain pen ink, the ink can smudge immediately after writing, making rollerball ink problematic for some left handed writers. Because it is a more liquid ink, rollerball and gel inks are not well suited for writing on coated papers. Rollerball refills will run out of ink much faster than ballpoint refills. It is not unusual to need three rollerball refills to do the same amount of writing as one ballpoint refill, but the quality of the appearance on paper is well worth it for those who love a rich, dark line.