Powdered herbs lose their potency fastest. Liquid extracts or tinctures are basically the same thing. Extracts generally have less alcohol content than tinctures. Extracts are very convenient and have years of shelf life. They are concentrated forms of herbs and one only uses a dropperful or less.
Powdered extracts are concentrated instant powders.
When put in capsules taste is not an issue and one still gets the concentrated strength. Another advantage to extracts, as well as teas, is they require little digestion and are easily absorbed. The use of essential oils is aromatherapy. Essential oils are mostly produced by distillation of the plant matter. They are the strongest form of herbs available today.