This is a long discussion with many different views and opinions.
It depends upon what you are taking the herb for and whether delivery of the active ingredients are via the blood stream in the case of tincture taken under the skin, or through the gut in the case of powder, capsule and tincture in water. The strength of the tincture is also important, eg is it 1:5?
It also depends on how good the source material is, its life, etc.
You read about the various types on this web site:
Do the capsules contain concentrated powder or granulated herb. If they contain granules then I would opt for the tincture. If you take the tincture with water then bear in mind that if the strength is 1:5 then 5 ml is equivalent to 1 gram consequently you'll need to take between 4 and 12 ml twice a day. A typical 4 fluid ounce bottle contains 113 ml.