Both hugely popular for their ease and convenience of writing but maybe you wouldn't know which is which? Well hopefully this can help.
The way the pens work are not hugely dissimilar. Both have a tiny metal ball bearing in the nib that glides around 360 degrees to evenly distribute the ink. However, it is the ink itself that differentiates these two pens, which we will get to later.
If you are trying to distinguish between the two from sight I would first look to see if it has a cap. Most rollerballs will have a cap, whereas ball pens don't and will instead have a push, click or twist mechanism. This is because of the ink each uses, which brings us back to the previous point.
Ballpoint pens use an oil-based ink which puts down a lighter but thicker stroke. Rollerball pens use water-based ink, more similar to that of fountain pens, giving a sharper, clearer line, flowing much easier. Water-based inks are prone to drying out hence the need for rollerballs to have a cap.
- More accessible so more choice
- Dries fast so won't smudge or bleed through paper
- Ink lasts a long time
- Ink will not dry out
- No cap to lose. Can be used with one hand
- Thick writing line
- Ink can leave blobs on page that can smudge
- Can be tricky to re-start if left un-used for a while
- Sharper, cleaner line
- Less skipping
- Less pressure needed for writing as the ink flows
- Ink can smudge
- Needs refilling more often
- Can bleed through paper
So now you know the difference between a rollerball and ball point pen you may want to know which is best suited to you. Well this would depend on what you want to use it for. Ball pens may be better suited for documents as they don't smudge or bleed, for quick notes or as a pocket pen. Whereas a rollerball may be better for writing for longer periods as the easy flow of ink will not induce hand cramps.
So you may find both styles will suit you best at different times and no one ever said you can have too many pens!