This answer is a bit complicated, because both brushes and combs can cause damage to hair.
Both brushes and combs have individual bristles. When hairs become wrapped around bristles, they create resistance, making it harder to pull the brush or comb through hair. In response, the person brushing or combing will usually just try to yank the brush/comb through - a big hair-health no-no.
While yanking the brush/comb through might seem like an effective de-tangling strategy because this feeling of resistance goes away, roughly pulling doesn't actually un-knot the hairs wrapped around the bristles. Instead, the tangled hairs are broken off or ripped out of the scalp. If your primary goal is just to get all the knots out of your hair quickly, rapid combing/brushing technically can do the job, but a decent bit of breakage will probably happen as well.
Ultimately, the strategies you use to de-tangle your hair may be more important than the tools you use to do it. Regardless of if you choose a comb or a brush, research has shown that being gentle while styling is key to preventing damage. If a knot is being tricky and refusing to come out, you may want to try gently de-tangling it with your fingers instead.
All that being said, it is important to remember that not all brushes and combs are created equal. According to unpublished Princeton data, some brushes and combs with more space in between their bristles may be less likely to create tangles. If you are in the market for a less damaging brush or comb, a model with widely-spaced bristles may be a good choice for you.
The Formulate Team