Both of these liners have calligraphy pen tips that are little flexible paintbrushes (versus, say, a felt tip).
|LORAC liner on the left, Physicians Formula on the right|
They both apply very nicely and make it easy to create a thin or a thick line. They seem to be equally black, and have very long wear-times.
|Physicians Formula on the left, LORAC on the right|
The Physicians Formula claims to have ingredients that encourage lash growth, but none of the ingredients on the list have any research on them to back up that claim.
I cannot discern any difference between these two. I wore one on my left eye and one on my right one day and forgot which was which by the end of the day.
These are both excellent liners, but the LORAC Front of the Line PRO is $23 and the Physicians Formula is around $11.